On my '71 340 back in 1986 an 850DP was 2/10ths quicker than the 750DP it came with.
Stock block, stock 2.02 heads, DC.590" solid, HS Dominator int., race hdrs, 4.30's/4200stall
max rpm 6300....I think you may gain as much.
I just can't bring myself to drop the coin for an 850ish carb and have it run the same,now if i got a guarantee it would pick up .2 i'd be there quick.