For all around street use, the 780 Holley VS would be great but, as a drag engine, with good rpm off the line, I think the 850 cfm, 4781 Holley DP with your manifold and the "D" cam would like each other more.
Possibly, but on my 428 drag engine, with a big solid flat tappet cam, I tried 800 & 850 DPs, a 950 3 barrel, 830 annular, 950HP, and a 1050 Dominator (with an adapter), and none of those ran any faster than my sorted out 780 vacuum 3310-1. Both with the transbraked automatic (5200RPM launch at WOT), or the 4 speed, launching at 6000-6200 RPM.Also tried 5 different intake manifolds (OFFY PortOSonic, Edelbrock F427 (ported), Victor, modified Streetmaster, and a port matched, divider cut down Sidewinder, and on my car, with my combos, nothing beat the Sidewinder /780 setup, EXCEPT when I tried a buddys Tunnel Wedge with 660s, which was worth 1 1/2 tenths and 2 MPH, back when there was the C6 behind the 428.