This is a welcome new part for the 3rd & 4th series Firebird & Camaro owners/ repairers.
On the outer frame as shown below lives the diff bump stops.. This will replace both for the price of less then one GM unit.
Rear Control Arm Bushing Kit: 79-85 RX7
Gearbox Mount: Explorer 96-01 V6 (+Bronco)
Master Kit: 86-91 Mazda RX7
Differential Carrier Bushing Set: 80-82 Corvette
Ball Joint: 58-70 UPPER various
Front End Links: 88-95 Corvette
Engine Mount INSERT: 98-01F V8 (LS1)
Engine & Gearbox Mount Kit: Ford 67-72 era V8
Body Mount Kit: 55-57 Chev Convertible
Master Kit: #128 - 2001-06 Various