The 650 is pretty old and beat looking and it's not a double pumper.
The 318 runs great with a 750.
I should wait and buy the 950 ultra for the 400.
Holley and all the other carb company's pricing is set so the bigger carbs are cheaper to a certain degree.
It seems the trend is to use a bigger carb and use annular boosters to keep the low torque better then it would be with down leg boosters.
I know with more rpm things change also.
I am one of the few who used a 750 dp on their 318 and if you have a good understanding of how the carb works, it can be done.
Most every hp build done in mopar magazine used a 750.
When they used the proform body,it was a 750 with down leg boosters.
I have been wanting to try a carb with annular boosters on my 360 because it's in a heavy car and at the same time be getting the carb for the new 400.
So many choices..................it's a good thing though.