i also used a 69 block and crank.you can use a later 440 piston or use aftermarket forged pistons like i did. mine are 90 thousandths down in the bores .i have edelbrock performer heads and that gives me an 8.2 to 1 compression.i have an 871 on but right now am only spinning it at 13 percent underdriven.i agree that an 871 would be better for a 440 and just underdrive it to get the desired hp. 600 is easily obtainable with a blower