I have a 67 GTX and it does not hook installed new slicks and it is not working like it used to the only thing I changed is the spring perches to install the 3 inch tti exhaust and I am wondering if I have the pinion angle wrong it went 12.03 at 112 with a 1.65 60 foot.The suspension is a factory leaf spring with out a snubber thanks for any help Matt.

Why did you have to change the spring perches for a TTI exhaust? The 60 ft looks decent, what did you run before? Is it spinning a lot?

list all the changes that were made in addition to what you mentioned, (if any)

The leaf springs had to be in the stock location for the tail pipes to fit.I had someone watch the first pass and they said it spun for the first 10 feet that was the only change to the rear suspension

it'd be work for sure but could you put it back to where it was (& working good) so you can see what the angle was then, so you can duplicate that # now? (& that was the only change correct?). EDIT or as is change the angle with some perch angle shims & see what develops.

First off how old are the tires? and how long has it been since it was at the track? Also did angle of the shocks increase when you moved the spring perches?