750 cfm carb on a 318

Large jet sizes are an indicator the carb is too big. If you're way above what the carb came with originally (factory jetting) then the carb you have is already a little big. Not saying you can't run a 750, but I'd stick with a vacuum secondary unit since they tend to "size" themselves to the engine they're bolted to.

That said, I don't think you'll gain much, if anything. The little hp you might gain wouldn't be worth the loss of driveability IMO.

Been there done that.