How do you pair up a "x" bore by "y" stroke master with what stroke/bore slave? Same criteria for internal slave vs external? Talking wilwood or tilton style aftermarket

pedal travel and ratio is going to come into play as well Need to be a bit more specific, IE: Talking wilwood or tilton style aftermarket
What? master or slave, internal or external?

If you go with a Wilwood pull type slave they can match you up with the correct master. Just about any master will work you just need to make sure you have an adjustable pedal stop to limit the travel. I have used a Howe master with a pull type Wilwood slave and they worked fine together.
Speedway Motors should be able to set you up with everything you might need
Gus

I'm asking which would be better... Currently the question pertains to an 85 D150 long bed, that has a /6 and a 727 in it, that I acquired all the parts to switch to an 833OD. And how to pick compatible parts.
The other site that I asked this in, is being quite ambiguous/vague in the answers I am getting. Like a link to "pascal". I dunno how that would help me pick components. And yes I realize there will be some custom fab involved in retrofitting.

All they say is call someone and get a "kit". I don't have no damn Chevys, like everything else Mopar were left to hang out and dry. What I DID see on the linked Brewers website, while it didn't answer my question, everything I saw said "only for use with a diaphragm pressure plate. I just bought a LuK and it's a 3 finger style. Didn't see anything in a diaphragm clutch listed for this one.
I also have an 80 volare, that I plan on going to a stick. Don't know what trans I will go with on that one other than it will have 3 pedals.
I do see in 87 the d series truck could have come with a hydraulic clutch. I have a used version of the stock setup here all plastic and seems chincey.
When I had a head of steam in the volare and was asking about retrofitting (if even possible) the late 80s truck setup to my volare I was told it was "cheap junk" and "not worth it" with no suggestions in what "would" be a good hydro clutch setup for
that one.

I see various kits for other kinds of cars and they just say "here. Install this pile of parts that we put together" with no individual specs for stroke or bore sizes for the parts they (randomly?) threw together in their "kits".
Swap meets are starting, and I'm going, and want some help trying to figure out whether I could put a "kit" together myself.

I don't believe you can mix the parts. You either use the hydraulic throw out bearing system, or you use the slave cylinder outside of the bell system.

The hydraulic stuff uses a diaphragm clutch cover (pressure plate) because they require less force to release, and that force is spread all around the entire center of diaphragm surface instead of just on the 3 fingers. The 3 finger pressure plate tends to be used in more heavy duty applications, but the diaphragm was used with a slant 6 granny geared truck trans in the mid 80s and most older 60s big trucks (but those were large diameter clutches).

The "hydraulic clutch" should be more accurately called a "hydraulic clutch linkage system". The clutch master cylinder, the hoses that connect the master to either the outside slave that moves the clutch fork which moves the regular throw out bearing, or to the inside the bell hydraulic throw out bearing which itself expands or contracts. A "kit" would be the master, the lines/hoses required, and either the slave cylinder on the bell, or the hydraulic throw out bearing inside the bell. Some places offer a "kit" that includes everything in one package rather then buying every thing separate.

The distance either moves is different because the internal hydraulic throw out bearing acts directly on the clutch pressure plate fingers (or diaphragm) because the bearing itself is what expands and contracts with the hydraulic pressure. The movement here is most likely under 3/8" (I haven't messed with many of these GM style set ups). Most oil leaks in that system are the throw out bearing and that dumps the hydraulic oil onto the pressure plate and disc.

The outside of the bell mounted slave cylinder basically replaces the mechanical linkage for clutch release with the hydraulic slave that normally pushes the clutch fork instead of the mechanical linkage that would push the clutch fork. The movement here on a Dakota set up is 3/4" (if I remember correctly). Any leaks here would be outside of the bell.

Both systems require a hydraulic slave master cylinder attached to the clutch pedal, and a line (most are plastic) that connects to either the hydraulic throw out bearing, or to the outside slave cylinder attached to the bell. usually the amount of stroke the master provides equals the amount of movement the slave/throw out bearing requires.

It may require some looking, but normally, the pressure plate can either be had as a fingered unit, or as a diaphragm unit with the same flywheel bolt pattern. GM used mostly diaphragm pressure plates, as did most 80s and later Mopars. Get the diaphragm pressure plate with the correct flywheel bolt pattern (at the pressure plate) and the correct diameter. I believe the assembled height (off the flywheel) are the same.

For the record, hydraulic clutch linkage tends to be a few milliseconds slower then mechanical clutch linkage, so there is a little more slippage when you dump the clutch. That does reduce some of the part breaking shock to the driveline.

If its mine, there isn't any way I'm installing a hydraulic throw out bearing. My coupe has a V6 with a Dakota hydraulic clutch linkage with a slave cylinder on the bell system. With a 3:55 limited slip and 225 75 R 15 tires I can smoke em in 1st, get rubber in 2nd, and get a chirp in 3rd. The "delay" I spoke of earlier, though I noticed, hasn't effected the clutch life much, this clutch has 100,000 miles on it.

You gotta do a few very simple calculations to come up with the required/desired ratio between bore of the master and slave cylinder.

.) what is your pedal travel at pedal pad (I'd say around 8")?
.) what is your pedal ratio (= distance from pad to pivot divided by distance from master cylinder rod to pivot)?
.) clamping force of the clutch?
.) ratio of clutch fingers?
.) ratio of clutch fork (if using an external slave cylinder)?
.) desired clutch departure distance (0.050"?)?

You can now do a back calculation.

Let's assume you have a 2500lbs pressure plate. Finger ratio of the plate could be around 5 to 1 (diaphragm is more like 8 or 10 to 1 iirc). Divide the 2500 by 5 and you get the necessary force to push down the clutch fingers (500lbs) - still a lot. The travel distance of the clutch departure (let's assume 0.050") becomes 0.250" at the fingers. This is without any free play though! Now you need to take the clutch for into account as well. A typical ratio is 2 to 1 - I don't think it's a coincidence that internal hydraulic throwout bearings also have a 2:1 ratio between bearing and master cylinder as they don't use a fork. That 2:1 ratio gives you 0.500" master cylinder travel (if the size of the slave and master is the same) - for internal TOB or external slave cylinder - and a necessary force of 250lbs to push down the master cylinder rod. Finally the pedal ratio comes into play: a 6:1 ratio would decrease the necessary force to around 42lbs and a pedal travel at the pad of 3" (0.500" x 6).
This is for a 3 finger clutch - a diaphragm clutch is way easier to push due to a different ratio but also requires more pedal travel. In reality the pedal travel is a bit longer due to free play. By playing with the size of the master vs. the slave cylinder you can trade off required force vs. pedal travel: a small master requires less pedal force but pedal travel becomes longer. When using a 3 finger clutch this is really necessary in my opinion as you do not use the Z-bar anymore which gave you a 2:1 linkage as well.

Let's sum up all the ratios: Pedal (6), Z-bar (2), Fork (2), Clutch fingers (5) = 6 x 2 x 2 x 5 = 120:1. That means clutch pressure of 2500lbs and 0.050" clutch departure travel will be 21lbs and 6" travel at the pedal (again, without free play). When using a hydraulic clutch you loose the Z-bar so you have to make up for it in the sizing of the master/slave combo. For example a 3/4" master cylinder paired with a 1 1/16" slave gives you that 2:1 ratio (you have to compare the piston area).

This is a very good read: https://www.novak-adapt.com/knowledge/clutches-etc/