here are the pics

Thrust angle is: if you draw a line through your centerline of the pinion shaft to the front of the car. You want that line to be perfectly centered between the front wheels, so the rear diff will be pushing the car straight down the track. It will be shown on the alignment machine screen as thrust angle in degrees. The panhard bar runs from the frame to the rear diff, from left to right. Thats what you'll use to center the rear end under the car.

Do you have any better rear undercarriage pics? That one is pretty much all brake rotor. :D

Center your thrust angle...the alignment shop should know what that is, you shouldn't have to explain that to them...if they ask what it is...leave and go to a different shop. lol

You simply want your rear tires to follow your front tires dead on straight, 0 degrees, zero'd out, etc...this will keep your car straight down the track, no counter steer, no dog tracking (when your rear wheels are both toe'd a certain direction causing the ass end to look like it wants to walk around the car to pass it. You will sometimes see old pickup trucks that don't appear to be driving straight, looks like the ass end is crooked....that's dog tracking.

Then I would just go with the others regarding your pinion angle degree...if it's off, you can adjust it using your upper bars on your 4 link.

If your four link is a parallel setup, it is not as ideal for drag racing compared to a triangulated four link, but it will still work fine. Ironically enough though, if you are a parallel setup, it's much better for handling. You won't get that locking effect that the triangulated rears have when you turn to sharp and the rear end just kind of pops out into oversteer. So ditch the Welds, buy some CCW's, and track it. :D

If I was keeping it I would buy some CCW's or similiar. When I was rolling on the Work Meisters, the car handled really good.