Carb Selection

I know this has been covered before but there is varied opinion on either a 750cfm or 850cfm for a 408.

My 408 build is

Magnum Engine
Probe Forged Pistons with eagle rods
Compression roughly 10.5
RPM Edelbrock heads
Cam Lift intake .568 Duration 236
I have both RPM Air gap and M1 but will use the airgap I think
3500 PTC Stall convertor 727 with 8.75 3.91 gears in a Duster

The double pumper carbs im thinking about are

Holley 750 HP
Holley 850 HP
Quickfuel Q750
Quickfuel Q850