I agree with Zip, more compression ought to wake it up a bunch.
Just curious since you didnt mention it >How much total timing are you running?
Dont be afraid to crank it on up there to the 39/40 mark with good fuel, that will give it more off the line grunt, something desparately needing.
Once again as Zip suggested the cam could be killing it.
Advancing it a couple degrees will improve torque down low.
As a comparrison : The boys 89 GT mustang (heavier) with a 351W and a small hydralic flat tappet cam and a few other mild mods sixties foots in 170's, mind you this car has a stock converter, nine inch slicks and 373's.
Best 1/8 ET has been in the mid 7.40's
With more compression/ cam timing and a steeper gear (456/488) - you should easily see mid 10's.
Goodluck and let is know how it goes, Cp