I would have a long look at the generator mounting brackets. There are differences between the years and car versus truck. Looks like a spacer has been added (red rectangle). I don't think the issue is with the water pump pulley.
Generator versus alternator. 6 volts versus 12 volts. A never ending debate.
If your old Stovebolt has worn piston rings and low compression, which many do, it's harder to start.
Converting to 12 volts can help spin the engine faster, raise the compression a little making it easier to start.
The main benefit is that it's cheaper than rebuilding the engine.
I am blown away by all the replies and insight on this. Thanks to all.
I noticed that spacer as well, I think I will start by removing that spacer to see if the belt lines up better. It's not too far off but far enough that it bugs me. I would have honestly left the truck 6v but the previous owner has already made the conversion. I might as well just button up the 12v as best I can. At least everything looks to be original!
