I probably shouldn't say this, but I'm going to anyway.....

Son, you may not hear from Pat again. Your question about roughest idle nails you as a poser because you're concerned with impressing the geeks at the drive-in with a ratty idle. Pat gave you his best shot, a cam with a very wide power band, reasonable duration for the static compression ratio so that the intake closing point matches up, long lobe separation angle for high manifold vacuum to operate accessories, excellent carb signal and reasonable valve lift for long spring life and easy operation on the rest of the valvetrain. He further estimated 500 ft./lbs. of torque from the motor. Horsepower will be unimportant in moving that big hulk of a Blazer. Pat knows what he's doing with big block Chevys, but I don't think he's too tolerant of youngsters yankin' his chain.