496
You can get more interest if you post your question under the ENGINE TECH section of this forum.
I can only talk about a 496 from a drag/bracket race combo.
320 heads like DART PRO 1 325 or RHS 320
119 combustion chamber.
12.5 compression.
Roller cam .725" lift, 276/284 duration, 110 lobe seperation. (Best to get a professional cam guy to make the selection once everything else is known.)
Single plane intake, Edelbrock Victor R.
1050 Dominator carb.
Forged crank and H beam rods with L-19 bolts. Eagle quality or better.
2 bolt block is OK with ARP main studs, line honed.
Best machine shop you can find.