Ford Wiring/Electrical :: 1996 - Wire A/C Switches To Shut Off Compressor Relay

I'm planning the install of a 1996 351w into my '77 F-100. I'm using the '96 accessory serpentine drive (FS-10 A/C compressor, '96 alternator, etc.). It needs to mate up to the '77 wiring. I'm going to use stock '96 underhood A/C components (accumulator, hoses, condenser).

As best as I can tell, the '96 system uses the ECU to manage the A/C system, but I've converted the '96 motor to a carb.

Looking at both the '77 and '96 systems I think the easiest underhood wiring solution would be to use the '77 compressor ON wire as a relay trigger, and use the '96 High Pressure Cut Off (HCPO) on the compressor manifold, and compressor cycling switch attached to the accumulator to interrupt the relay output to the compressor.

I can get the switches and pigtails, and I can look up their pressure trigger points, but I don't know the voltage the '96 switches operate at (12v or some reduced voltage?) or how to simulate their trigger conditions to see how they work. I guess that at ambient pressure the HPCO should be normally on and the cycling switch should be normally off. So I could just wire them into the relay ground or trigger connection. But of course they aren't simple two wire switches. (Edit: Looking at it online, the cycling switch appears to be two wire, the HCPO is 4 wire).

How to wire them, should I use them to interrupt the relay ground or trigger connection?