Saw your question last night, can't believe it hasn't been answered by one of the "experts"......which I am not. Anywho, your spec's sound like this is a pretty hot build but you didn't indicate what it is for....mostly street, street/ strip, strip only, weekender, hopefully not a street racer
With the smallish heads I think a properly built and jetted 750 would work pretty well. Try that out first, you can always upgrade to larger carb but again it all depends on the application. I'm going to be running a Quick Fuel 780 on my 507" Cadillac, big engine but the rpm limit is around 5,000 so i think it should work. A lot of this stuff is trial and error.....good luck.