Not real familiar with C-6 configuration however if there's a possibility of reattaching your existing and in place diesel C-6 to the 300 six banger, that would be the easiest route. Somebody here should know, "are C-6 bell housings removable"? "Is there an adapter designed to connect diesel C-6 to 300 six"? Can you or someone local fab your own adapter? Swapping just the engine would eliminate many hurdles, especially if you also converted the 300 six to a carb. I think 300 six has the same bell bolt pattern as 289 & 302. IMO, 300 six is a great truck engine, not speedy or overly powerful, but a very good robust design if longevity and low end grunt are what you're looking for. Suggest changing oil filter housing to the older style which positions it vertical. Later models with horizontal mount seem to "knock" when you first fire up.
