What is your meaning of "6 pack heads" even if they were true offset rocker heads it would not make any difference weather they were t/a heads or 318 smog heads with the problem you describe.

How many miles on the motor

Have you pulled the vac hose off the power booster and plugged it to see if it helps, a bad diaphragm in booster and even the vac can can be a hidden bug.

I would swap the disturber and if no change id re seal the intake, then if no change look at the common little gremlns.