UMI’s solid motor mounts replace the factory rubber motor mounts decreasing engine movement for maximal vehicle performance. Solid mounts bolt directly to the frame of the 1974-1992 Camaro/Firebird and 1978-1988 GM G-Body as well as many other 1974 and up GM V8 applications.. Solid mounts are required to be used in conjunction with factory block mount clamshells or UMI’s P/N 90058 clamshells. Note: Centerline is 1" from cross member surface to center of hole. Check your original parts dimensions before ordering. Solid mounts may not work with Oldsmobile V8 style clamshell. Crafted with pride in Philipsburg, PA- USA.