Installing a Tremec Transmission in your Mustang? Then you will need a drive shaft spacer to make up for the difference in length or get a custom made drive shaft to make up the 3/8-5/8". Our 5/8" Billet Aluminum drive shaft spacer makes up that difference and includes longer hardware for a seem less installation. Being made from Billet Aluminum means less rotational mass and will keep your drive shaft at the proper length to prevent yoke failure.