Chris, if you're committed to remaining with a generator-charged system and if this is an AD or Task Force truck, there are Delco-Remy voltage regulators and there are all others. I think you should ignore the "all others." Honestly, many of the Delco-Remy 12V regulators made for vehicles between around 1957 and 1964 should work just fine. I'd go to eBay and search. This one (for example) ought to be okay for you:

https://www.ebay.com/itm/303782651554?hash=item46badb66a2:g:l-wAAOSw5XVfvdfa

I'd go to eBay and look for NOS Delco-Remy voltage regulators (if it doesn't say Delco-Remy, I'd ignore it). There will be some new old stock (NOS) ones which are selling for less (may be shopworn) and some selling for more (may look prettier). You could find one specifically matched to your generator, but I'm not the person who would say you'd need to do that. All the voltage regulator does is to maintain the output of your generator to somewhere between about 13.5v and 14.5v. This lets your battery charge (and stay charged) at the proper voltage and to ensure the other electrical parts of your truck get the proper operating voltage. Good luck.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end