Not sure what carb your're trying to retrofit. I swapped proform blocks onto my QF 750HR 4150 double pumper. Works great. Check the gasket openings between the block and the main body. The block to body gasket should seal off the spot on the block where the main well transfers fuel to the idle well. That transfer spot should not overlap with any opening in the gasket.
You'll need to tune that billet block to work correctly. Typically move the IFR to the lower position, and block all but 2 of the emulsions to mimic the behavior of the old holley configuration. Thats typically a good place to start.
https://forums.maxperformanceinc.com...ight=quickfuel