Easy way to wire the relay so the relay turns off with either ignition key or cut-off switch, you could run the relay ground through the one side of the 4-pole cut-off switch, and power the relay from the key-on ignition power.

I think the reason for not allowing ground side disconnect is that it only can be done for the battery.
The alternator grounds through its housing to the block. So the engine could continue to run and the alternator keep making power.

Cab's method would not have to result in a hot alternator wire if a single throw, double pole was used.

Nice! That avoids the need for a second relay.

I like it. Thanks very much for the input guys!

In the OP, those are NOT two ford style starter relays in the schematic.

One is a ford starter relay, the other is a continuous Duty relay in the the alt line.

Just a small clarification.

The weight thing is great, there probably isn't 5-7 lbs difference in any of those approaches and some are much safer than others. Go on a diet, I've seen some of you! LOL There is more to be gained from that approach than skimping on a wiring approach!

Just to follow up on this:
Crackedback posted a picture and diagram of his setup which uses a remote starter solenoid (aka Ford solenoid) over on FABO
https://www.forabodiesonly.com/mopa...isconnect-wiring.454312/#post-1972828436

A point was made in that thread about keeping main lines short, but also that its best not to cut the alternator output while running led to combining this into diagram.
Putting the ignition circuit onto the relay instead of the alternator output also greatly reduces the maximum load on the continuous duty relay.

Drawn here retaining the ammeter and factory wiring.
A heavier or second alternator output wire goes to terminal stud.
From the stud is
one connection to feed the ignition through the relay,
one connection to the battery
one connection to an auxilery fuse or breaker box for electric fuel pump and maybe headlights.

On my Duster I decided to avoid the whole mess so I put a lightweight battery in the stock location. If the battery is located in the stock location then I don't need a master cutoff switch and I don't need to run a bunch of cables back and forth to the trunk.

what did you use for a battery, and how many [cold ?] cranking amps is it ?
how much timing do you run, and how does it crank over hot ?
i'm guessing you are using a mini starter ?

I found out the hard way that this method does not work when the alternator output is grounded, the standard battery cut off switch does not isolate the alternator wire from the batteries allowing that wire to be hot all the time
I'm going to switch my battery cut off switch it to a type that will isolate the alternator and kill the ignition when turned off as well
I found out that my cars battery cut off switch would not isolate the alternator feed wire when I accidently grounded out that wire at the races by hooking up by timing light hot lead to it with the motor not running at the races and then starting up the motor which vibrated that clip over allowing it to ground out on the alternator case smoking that 10 gauge wire completely all the way to the battery hurting some of the other wires tie rap to it My single pole, single throw battery cut off switch di dnot isolate that wire from the car
I run a Powermaster 100 amp one wire alternator on the car and was told by a tech at Power Master after smoking that #10 wire to run a #4 wire from the alternator to the battery connection and to make sure and ground the alternator from the threaded ground connection on the back of those alternators with a #4 also to a threaded bolt hole in the block
I have done that part now
My next wiring job is to find a better battery cut off switch to use to prevent this happening again!
Can I ask for a part number and brand of one of those

Cab.
You could use your single pole kill switch if tech is OK with just a battery cutoff.
To prevent what happened, put a fusible link or maxi-fuse in the alternator output line.
Should be one on every larger wire connected to the battery.
That way if any get grounded, the fuse or link goes automaticaly.

The only wire that carries too much load to use a fuse or link is the one to the starter.

if one uses a fuse on the alternator output, how much larger than the total output of the alternator should the fuse be ?

Maybe Crackedback will chime in.

With a fusible link its not so important what the alternator rating is - within reason.
Go 4 numbers (2 common sizes) smaller so the link burns up first.
If the alternator output wire is 8 awg, then a 12 gage fusible link will melt first.

You can see that's what AMC did starting in 1986.
http://www.heritech.org/wagoneer/mggw5a.html
Whether the J-truck or grand Wagoneer came with a 94 amp alternator or a 78 amp 12SI, or a 15Si model - they all got the yellow fusible link (I think that 14 but maybe 12 gage) on the alternator output wire.

With a maxi-fuse, I still don't think it matters so much what alternator rating is. Or maybe a better way to say that is the alternator rating is secondary.
The fuse is about protecting the wiring and connectors etc. Just like house wiring. In a building, the fuses or cricuit breakers are sized based on the wire and the load. if we use 14 gage wire, we must use a 15 amp breaker. If we use 12 gage, then we can use a 15 or 20 amp breaker. But if we expect to be putting several heavy draw devices on that 12 gage circuit, using the 15 amp breaker might trip unneccessarily.

There's some examples comparing fusible links to wire and use in the FWD mopars.
http://www.minimopar.net/electrical-links.html

the Pacific fuse seems to be a good alternative to fusible links.

You can see why I like the shutoff scheme I posted above. It avoids putting a link on the alternator output. Just needs the one link on the battery charge/feed line. At some point that has drawbacks when lots of electric equipment is added. But for a car that mostly uses the battery just for starting its a simple solution.

I don't recall ever seeing a 4 pole switch that will handle the potential current of an alternator. Most are rated at 20 amps or less on the small poles. I also prefer separate components in case of replacement/failures arise. A four pole fails, you are in a tough spot. If a CD relay fails, you can jump it and be no worse than the minimum standard in a pinch. In 20 years I've not had a single CD relay fail on a car... knock on wood.

A fuse equal to the max rating of the alternator + some overhead would be OK in a charge line. I prefer a fusible link and use them in my wire around set ups.

I see a lot of objections regarding weight considerations in different wiring diagrams that are safer. I believe the differential from the minimum standard to a very well thought out safer approach is under 10 pounds. As a note, 20 feet of 6ga welding cable = 3 pounds! 1/0 is about .40#/foot, 2/0 is .55#. It's insignificant weight to the ET of a car that isn't being flogged for every hundreth. I know class guys that use an approach like mine, because the safety and peace of mind outstrip the weight factor.

Pick your parts, pay your money

I totally rewired the Challenger a couple of years ago using two painless wiring systems, a stock one and a 10 cct (?) race one for the electric fuel pump, water pump, big fans etc. Best thing I ever did, I used a 100A solid state relay that isolates the supply / feed to the 1 wire alternator so only 2 of the poles on the cut out switch are H/D. I also ran a neutral "Ring" around the car with 6 strategically placed bus bars for electronics - ve and earths rather than use the chassis. Also ran an extra -ve cable to the starter motor and earthed the heads. All lights barring the headlights were replaced with LED's. The Engine side looms were also" hidden" for a cleaner install. It all worked out well.
Before

After