Rear end spins out to the left.

[vector1]

I would check to make sure everything is square. You can find details in any stock car book, etc. I would use plumb bombs and find the centerline of the chassis or at least the center of the front of the chassis, then drop a line off each rear hub with jack stands under the axle, make sure the arms from the center front point and each rear tire are equal, you can also use this to adjust the rear end left to right in relation to the centerline of the rear of the chassis. With everything square on the car and in your mind you can move on to other possibilities. If you take it to an alignment shop they will do the thrust line off the front uprights or suspension when they check caster. Your choice on how you want to do it.

If the weights are adjusted for road racing as you say, I'm assuming you are referring to cross weights being 50/50. To get the cross weights equal the left and right rear tires are not going to be equal in weight, you can make them equal, but then when the front comes off the ground things change and you have to account for your ass. I'm not a drag racer so don't know if this comes into play, but I would check to see if everything is centered as described, that will prob fix a lot of questionable.

Nice pic btw.