Nathan, I had to go back and look at what I did. At first I tried using a large cap HEI that was given to me, that turn into a massive oil leak. I just couldn't get it to seal at the block. After doing my home work, I found that the reason the factory distributor has 2 grooves in the shaft is to stop the oil from migrating up the shaft. Lesson learned.
At this time I had removed the engine from the 1960 C10. The 235 had a small cap HEI, it looked very similar to the Tom Langdon units I have seen. Looking back now it did seem the drive shaft was as you describe, shorter. I crossed the numbers and found it was from a GM 2.8L. The module was bad, taking the old module to the FLAPS they crossed it to a 1983 2.8L S10. The HEI had a GM square type coil, I opted to use the "Flame Thrower" I had. I installed the distributor in "Thor", completed the wiring and never looked back.
Needing a distributor for the 1960 235, I again turned to Rock Auto. The GM 2.8L was used in countless vehicles. I found a listing for a 1985 Jeep Cherokee, it showed distributors with and without vacuum advance. I have ordered the distributor and waiting on it to arrive now, it should be here today or tomorrow. To compare the two I would need to pull the HEI from "Thor", that's just not going to happen right now.
In the Electrical Forum, Jon G has a great write up on converting a 230 HEI for use in a 235. I know that Deve's web page also addresses this, our own HRL has some great input on the subject as well. I will post some pictures once I have the new distributor.
https://www.rockauto.com/en/moreinfo.php?pk=3863862&cc=1179569&pt=7108&jsn=585https://www.rockauto.com/en/moreinfo.php?pk=1123678&cc=1179569&pt=7108&jsn=586
