Traction Issue

I just had my local machine shop install a new 512 440 Source stroker kit into my '70 440 block. The car is a 72 Challenger w/727, 3000 stall converter & Strange 60 rear w/3.23. I put the largest tires on the back that clear the fenders (255/50R17 Nitto).

The issue is when I go around 30 to 40 and nail the gas the car often pulls quickly to the right so I can't stay on the gas and keep control. I had replaced the shocks & leaf springs earlier and all is new. The car brakes straight so don't think the right brake is dragging to cause this.

Any thoughts?
diff tire height will cause that too , have you actually measured them ??
we used to have to keep our slicks (under) 1/4'' differance , or the car would go to the side with the shorter tire heighth , when the front wheels were off the ground ...