About 30 years ago I put a 518 in an 88 d100, mine originally had a 904/998/999 3 speed, but had the electric activated Lock up. I remember having to go junking for a cross member for a newer version of that truck. Also 88 was the first time you could get a 500/518 factory equipped in a D/W series trucks. so as I remember, I got the parts that were different from another truck and put them in mine but that 88 had that miserable TBI system,
my 85 is staying carbureted.
As I remember that 88 would have LU and OD kick in simultaneously. (Since I added it in, and wasn't factory equipped in that particular truck) I don't remember exactly how I did the wiring. But I know I didn't run anything thru a 5v anything, as newer ones run/ I used strictly 12v.
As I remember, that was already 30 years ago, I've slept since then.
Most I see for "kits" out there specify a certain speed for each to kick in. As we all know all driving situations aren't identical. So id rather have LU and OD kick in seperate, and not a time interval (one of the replies to my original request said "LU is 10 sec after OD kicks in" as an example) but I don't know if a set 44 mph or 50 mph is right for all situations either. Id like to have it vary based on amount of throttle input just like the current 727 does, and passing gear to work like it should.
If I get the "50mph option" for OD and the "52mph" LU, what would happen if I were to punch it? Would it go from OD-3rd automatically, or OD drop to 2nd automatically, and if it went from 4-2 with drop down would it upshift from 2nd right to OD and LU all at once when I let off the gas? Id want a more natural progression of upshifts and down shifts than that.

I'm currently bouncing around ideas in my head, (don't laugh/ it's a /6 currently with a 727 in it as stock, but I have built up the /6 a bit.... No plans to V8 swap.) Truck has a 3.21 rear in it as stock. I may eventually swap that to a lower ratio but not at present time.

I have either an 833 OD with everything else I would need to swap that in, and I have this a500 along with the adapter plate as used on 60s /6s that used a 727 since back then they didn't have a dedicated 727 case for the /6 so they used a SB 727 behind the /6 which is how it comes that I could even put the a500 behind this motor.

I'm debating which way I want to go with this truck, and have most of the parts for either option.
Well, I have all the parts if I decide to go stick, and all but the right length drive shaft, rear mount parts and whatever I'm gonna need to make OD and LU work as they should to use the a500 if that's the way I decide to go.
I'm asking these questions just figuring out what I'm getting myself into for this option since I have "most of" what I am gonna need on hand already.