I'd say right at 590, you've got bigger headers and heads and a bit more lift than my little 414.

Cam's in a little early and tight centers which is gonna make massive moves through the middle but the torque may not hold on long enough to get the really big numbers (over 610 or so) up top. That's where I'd put it in a 3000 pound car but I'll bet the rampage might ET bestter with it in a little later, especially with the big headers and the 5's

Never ran the large port M1, I like the Vic 340 ported with the 2" HVH/Wilson 4 hole on mine a lot, I think the short runners of the vic are an advantage on the long stroke short rod ratio combos when the cross section of the port is still fairly small.