71 valiant engine build, which carb to use

So a few months ago we had to pull the 318 engine out of my son's 71 valiant 2dr. The thrust bearing had failed, wiped out the crankshaft. Block was magnafluxed and deemed worthy for a rebuild. Original block to the car, we had a crankshaft out of a 68 318 turned, the block had to be punched .40 over, he bought the forged scat rods, kieth black hyperutetic pistons, mahl bearings throughout, and of course the edelbrock aluminum head, air gap intake, cam, lifters and timing set kit. The machine shop did a full assembly, file fit everything. Line bored, balanced, etc. The question is what is the best size carburetor to use. He has fairly new 600cfm edelbrock avs, the edelbrock kit came with a free 800cfm Avs carb. I'm thinking the 600 is too small and the 800 probably too big. The kit came with choice of a 600 or 800, since he had a new 600 he opted for the 800. Cam size is @.50 234int/244exh advertised is 308int/318exh 2.02 intake valves 1.6 exhaust valves the machine shop is estimating a 10.1 compression ratio. Any thoughts on proper carb size? I ran the standard formula for it and it lands near 600 cfm with that, but not knowing exact Volumetric Efficiency, rpm max, I could only put in assumed numbers. I would think it would be better suited with at least a 650 cfm. Lol, I told him efi would be the best option, but he likes the old school carburetor.