Monday evening, I swapped the best of the two spare lock barrels onto the Travelall to test out the theory that the continuity problem might be an issue with the lock. Comparing the connections on the back, I swapped the wiring as it was on the current assembly and sadly, I got the same result—the Sniper head unit rebooted itself. Upon further investigation, I looked over the diagram from the service manual and identified the main circuits going to each of the poles on the back of the assembly. From what I could tell it was  mostly connected right, but my 27 wire (going to the speedometer, and then on to the fuel gauge) wasn’t on the right circuit, I needed to verify that the white wire in the center was the 14 wire (going to the starter), and verify the black wire on the ignition pole was the 12 wire (going to the coil).
Disconnecting the battery and checking things out, I put the 27 wire on the right side and verified the 11 wire was correct. The wire to the starter was not an original IH wire and covered with electrical tape, but I’m guessing it’s the right one in the right place. I ordered a Bosch relay, which should be here tomorrow, and I’ll wire that up to troubleshoot the Sniper this week.
I do have to say, it’s very nice to be able to unlock the door and start the truck with one key.
Later, I pulled three starters from the Heavy Spare Parts Pile to test them out, figuring I might eventually have to swap one of them in for the one on the Travelall. I’ve got a 12 volt bench tester, which makes this kind of thing very easy, so I just lined them up on the bench and connected the positive lead to the main connection and grounded the chassis. With a short length of copper romex I jumped the power to the start terminal on each one, and found that one was completely dead, one didn’t move but made an alarming buzzing noise, and one (that came to me with the solenoid cover off) punched the starter gear forward but didn’t spin the motor. So I’ve got two good cores and a third that might work in a pinch. I forgot to whack on the buzzing unit with a hammer to see if I can wake it up, but that will be a tomorrow test. And as I recall, there might be a fourth still attached to the spare motor in the garage…