I have a 348 Spider with a *rocking* driver's seat. I need to fix this. Any advice please?
There's at least one thread in the archives about rocking seats in the 348. I believe the Spider uses the later style mechanism with the teeth on the outer perimeter of the adjustment wheel. If the teeth are shot, you're out of luck. If the allen head screws are loose, you can make considerable improvement by tightening the screws after the seats are removed from the car (not too difficult, you might need to buy a tool or modify an existing tool to do the job - less than $10).