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.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
