Prestolite Ignition Question

I have a 1976 Pacer and I recently bought a 1975 Pacer.

On my 76 Pacer, I converted the ignition system from the factory Prestolite electronic ignition to a homemade setup using a GM HEI module and a post-1977 AMC factory electronic ignition distributor manufactured by Motorcraft. I added the wide HEI-style distributor cap, along with the accompanying cap adapter and rotor, that Ford started using around 1983 for their six cylinder engines, along with an MSD Blaster 2 coil, NGK Iridium plugs,and a good set of Taylor spark plug wires. It works great.

My 75 Pacer was sitting in a basement for 15 years before I got it. Among other weird things about it, I discovered that it had a points distributor in it. There is a Prestolite-style ignition box sitting on the fender, disconnected, and all the Prestolite system wiring is still there, so I assume it came from the factory with a Prestolite electronic ignition setup and was converted over to points at some point. It took me a long time to get it to crank (I ended up replacing the starter and the starter solenoid and even then I had to ground the solenoid with a jumper and jump it off the battery to get it to crank: I'm pretty sure both the ignition switch and neutral safety switch are bad), but with the points distributor installed, there was no spark. Now granted, maybe I didn't give that setup a chance to work, because I made no attempt to set the gap on the points or check whether the condenser was ok, but I messed around with points for the last time over 25 years ago and I'm not going back. So I decided to install the factory Prestolite system that I removed from my 76 Pacer.

I am on the verge of trying to start it. I have so far replaced the coil with a used but working MSD Blaster 2 coil, installed NGK iridium plugs, a set of factory replacement spark plug wires from Autozone, and the used Prestolite ignition control box and distributor from my 76 Pacer, which worked. I am pretty confident in my abilities to read a wiring diagram and do stuff like keep track of firing order when swapping a distributor, so I'm not worried about having made any mistakes there. However I do have one issue I'm worried about: although there are two wires leading from the ECU to the distributor, there only appears to be one wire between the distributor and the connector that connects to the ECU. Remember, this thing ran, and I don't think I broke off a wire. Is this normal?

The only reason I can think of for this wiring configuration is that the second wire is a ground that typically runs back through the ECU, but my distributor grounds itself directly to the engine block. If so, this could be a problem, because I noticed that the points distributor had a gasket on the mating surface to the engine block whereas the Prestolite distributor from my 76 Pacer did not, so I transferred the gasket to the Prestolite distributor. This will probably prevent it from grounding through the distributor body.

Does anyone know if having one wire between the distributor and distributor connector is ok in this situation?

Thanks!