Car won't go straight with southside machine lift bars
 

I have a car that I built for a freind of mine and we took it to the track on 5-18-02 and with street tires on it the car went straight but when we put on slicks the car went straight until third gear. First and second gear it went straight but when you hit third gear the car's rear starts to the left hard and you have to get out of it to ever get it straight again. It goes so hard i almost hit the wall.
Has anyone had any experience like this and if so how did you correct this condition. Slicks were set at 12 psi and they were M/T ET drags. Any suggestions will be appreciated.

weld the plates
 

Did you weld the plates on or bolt them on???

I've run southy's on 7 different 5.0's and never had a problem, except that "clunk" common with all southsides.

My opinion is, if your control arms were the problem, it would happen all the time, everytime, right from the get go, especially on launch, as they would be "loaded" the most then, and rebound with a problem then, purely guessing here.

I suspect a rear end problem associated with a certain speed.

Or...how about very low tire pressures?

Although i don't believe this is the case here, I am involved with proffessional racing everyday, and many F1 and Champ car drivers have complained of pulling this way or that way, and telemetry shows that the driver was actually "pulling" the steering wheel, causing the drift, trying to compensate for G forces applied to him, like I said, I dont think thats the case here, but you need to look "outside the box" here, because the description of your problem is really weird, but I love the weird ones after doing the common ones to death.

Hope this helps;)