Is this a SBF? Cleveland? What kind of heads? I heard of some problems with the early Ford Motorsport aluminum heads before?
Sounds like a cool car your running and Willow Springs has got to be my favorite track. Too bad I'll probably only get to drive it playing Nascar on the computer. Hmmm I wonder if I can download a early Cougar car mod for the game.
A few more ideas, have you checked the advance timing to make sure it's working, the old Ford style distributors with a set of Mr. Gasket advance springs would sometimes stick advanced if the stop was set too far. Make sure they are free and loose and don't stick with the springs off. No worries if your electronic.
Keep us up to date.
P.S. Some in car video of a sliding Vintage TransAm Cougar coming through the corkscrew hard on the gas just might give me a heart attack.