I have a new 650 dp that I am planning to put on my 350. I am expecting close to 400 at the crank out of this ( the gmpp vortec 350 with upgrades). I assume that once I learn how to tune and get the proper jets I will be fine. It seems as most people are sticking 750s on such setups, my "old school" friends seem to think the 650 will be fine however.

 

Yeah, a 650 will be suffiecient. you might see a handfull more horses going with a 750, but I wouldn't predict the difference will be much.