Carb choice for high altitude?

I currently have a 625 cfm Carter AFB on top of my built 360 with Magnum heads and am considering getting a Holley double-pumper to use when I race the car. I have read people have had good luck with 750 cfm carbs on 360s BUT I also read that engines don't need as much carb airflow at higher altitudes; I am at ~6000 ft. above sea level so would a 650 cfm be a better choice? Here's my setup I intend to have once I start racing my car at the strip:

Engine: 360 LA block bored .060", factory iron (untouched) Magnum heads, KB flat-tops for 10.5:1 compression, Voodoo 256/262 dur. cam (hope to upgrade to Howards 275*/.470" cam later on), Magnum Air-Gap intake, and Hedman shorty headers.

Driveline: 904 trans with factory higher-stall converter (2200 RPM I believe) and shift kit, maybe upgraded internals if I blow up my current one :glasses7:... also 8 3/4" rear with sure-grip and 3.91 gears, I may give slicks a try depending on how well my street Firestone Firehawk Indy 500's hook.

This is in a '70 Duster btw