These motors are pretty hard working... After I put my trans back in the car was never running quite right. At an idle it sounded great, but it just didn't have a lot pulling power going down the road. Then after warming up the motor would shake really bad. After using a recent thread about the MSD dist. I swapped the springs and the advance bushing and rechecked my timing. I start reconneting plug wires to the cap and I realize that the 3 and 4 plug wires were switched 
I've been driving around on 6 cylinders for the past few weeks and didn't even realise it. Got that switched and now the car runs great! - John