disapoining et

When you pulled a plug, where did you pull it from? Did you pull a plug from the 7 or 8 hole to see what they looked like? I bet they look different than the 1 or 2 holes. This is where you'll see an issue with jetting imbalance. Another member had the same thing with jetting and the car wouldn't run like he thought it should, 13 step difference, got it narrowed up and the car picked up. You have roughly a 10 step difference with no power valve, which is huge... You're feeding the front half of the engine a lot more fuel/richer than the rear half.

Advance springs - take off the garage door spring if it's that huge one that originally comes on the MSD. Put 1 light silver and 1 blue spring on it. Those heavy springs wreak havoc on timing curves in those distributors from what I've seen. At idle you should have about 18-20* of timing. The engine should idle pretty easily at 800-850 rpm in p/n and only drop about 50-75rpm in gear.

Good luck with it.

P.S. Beatniks carb is a much better choice than the one currently in use.