Launches right, dives left

Took the Shelby Dakota on its maiden voyage before turkey dinner on Thursday. Never felt this issue before in any vehicle I've had.
Wants to pull right upon acceleration and dive left upon letting off the gas, no braking involved. The dive left is more pronounced than the pull to the right.
When braking, hard or easy/normal, stops true and straight.
The only suspension work that was done for the rebirth, was adding a 2 inch lowering block to the rear so the truck sits level. I've gone back over the ubolts and blocks - everything is tight, centered and where it should be.
Would an altered pinion angle cause this?
Ideas?