Sorry. I am not familiar with the shops in sacramento. The people I know who race vintage or open track events are either from the east bay or south bay areas.

Since you indicated back issues and the car kicking out, it sounds like your suspension does not have the ability to absorb bumps. It never hurts to check the torque settings on the lug nuts (80 lb-ft), but if some them were loose - I think you would have had a bigger issues by now such as losing a wheel.

 

First question, who did the install of the springs and SPC kit, was everything installed correctly.
Second pull out a rear shock as they are the easiest and see how it rebounds when you push on it and check if it is dead.
Third get an alignment