JEGS Billet Aluminum Mustang Driveshaft Spacer is designed to allow the use of a stock length driveshaft in 1979-04 models when performing a transmission swap from a T-5 or AOD to a Tremec or C-4. Maintains proper tail shaft engagement. Reduces the risk of slip yoke and u-joint failure. Eliminates the cost and time involved in ordering a custom length driveshaft! For use with 8.8" solid axle (non-IRS) applications. Includes grade 12.9 hardware for strength and durability. Made in USA.