What is your cylinder pressure? Get that first so we know what your working with.

My friend's 68 4 speed GTX w/ 3.54 drove like it was on ice in 1st gear. Small cam, fairly low cylinder pressure, good factory heads, factory spreadbore intake and matching carb. Car was a blast on the street. That being said, it really wasn't that fast at the track, so don't confuse the two, as they may or may not be the same thing.