I have a '90 lumina and the front upper motor mounts are shot. How much would it cost to replace them at a auto shop?
Depends - expect labor to run anywhere from $80 - $200 and the mounts themselves are relatively inexpensive. It's a fairly easy job, perhaps you might do it yourself and save the labor $$$. This mount is commonly called a 'dogbone'.
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1988 9C1 - Modified LM1 @ 275HP/350TQ - TH700R4 - 3.08 8.5" Disc Rear - see it at http://www.silicon212.org/9c1!