[I do have a set of 4:56 and 4:88 both sure grips. That would surely get it screaming]
I saw my brother at a superbowl party last night and talked to him about the Aspen I mentioned earlier. The only difference thats obvious in your combo and his is the compression, he's at 12.5 with some Ross pistons and you're at 11.1 with possible TRW's. The slick on his car is 28 inches tall and he shifts at 6000 and goes through the traps at 6000-6100 at 122mph on average. The gear is a 4.10 like you already have in your car. The only thing we dont know is the weight of ur ride and unless its unusually heavy I would start looking into the tune up for the loss of MPH and ET. Looking at some calculations at that speed and rpm you should have a 4.30 or higher in the car. The speed and mph you have given us should show a 5500 trap RPM. Too much converter slippage??? Who's it made by and what condition is it in?