Can it hook?
IMO,
Snubber = Door stop. Don't need it on a good SS spring set up. Clamp the snot out of the front segments and loosen up the rears. The rear shackle angle is CRITICAL to proper operation. Is the pinion angle right?
Make darn sure the rear shocks are long enough.
It will be easier to hook the auto than a 4 gear.
1.9 60's is not good. It only runs 112 mph with the 500 hp engine? Something isn't right! 500hp at 3300 should be in the 120 range at a minimum is my guess.
With a good set up and a 4500 converter, that car should 60' in the 1.4x range.