650 dp vs 750 dp in a 408

He just said that it pulled harder. That is subjective and not anything you can measure. It is not a race car. We don't know anything about the car except it has a 408. Not much info. CR, heads, Cam, intake, exhaust. gearing, tire size, vehicle weight and on and on. Just a lot of assumptions when giving "advice" Carburetors work on demand. The actual flow depends on many variables. Remember that you can only flow in as much as you can flow out. Engine is just an air pump.