First off yes, 750 is too much carb for a stock 350. It can be used but hard to tune in. I wouldnt go bigger than a 600. The other problem I keep seeing is when people set up a carb many of them set the idle circuit way too rich so it almost gives a loap like its got a big cam in it because it "sounds cool" If it drives down the road ok and you want to save money then rejet it and tune it in right.