I HAVE A 70 COUPE 350/300HP AT. MY CAR SITS JUST A LITTLE LOW ON THE DRIVERS SIDE (NO SMART REMARKS! HAHA) JUST ENOUGH TO NOTICE FROM TIME TO TIME. WHAT SHOULD I START TO LOOK FOR THE CAUSE? IT DRIVES,BRAKES,AND ACCELERATES STRAIGHT IF THAT HELPS AT ALL. DOES THIS YEAR HAVE ANY KIND OF A RUBBER BISCUT IN THE BODY MOUNTS THAT MAY BE ROTTED AWAY?

 

I would start by looking at the body to frame bushings. One may have fell apart or fell out.
If that's not it I would look at the springs front and rear.
Rembember the car is 36 years and so are the parts that hold it together.
Also, you never know, it could be a tire.

 

I have a 69 350/350 and it had the same problem. I replace all the rear suspension rubber and bolts and it fixed my problem. I believe it was the control arm bushing.