The double pumpers are a race oriented carb and are very, very rich for street driving. They work good but will wash down your cylinder walls and foul your oil without a good bit of re-work on the transition and cruise circuits.

850 is a good CFM range for 451". But a more street oriented carb would be better suited to the majority street time the car is intended for.

Either way, some tuning will be in order. But a street carb should be closer OOTB than a race carb for a predominately street car.