1978-1988 GM A/G-Body LT-Swap Crossmember Add-on Bracket for 6, 8, and 10-Speed GM Transmissions. Use with 12644HKR-1 Trans Crossmember and a standard GM Transmission Mount (71223029HKR, 71223030HKR, or 24350) as well as the following adapters if needed. 12644HKR-1 – Transmission Crossmember (no additional adapter needed for TH400/200R4/T-56/Magnum) 12655HKR – 4L60/65/70/75 Transmission Adapter – use with 12644HKR-1 12656HKR – 4L80/85 Transmission Adapter – use with 12644HKR-1 BHS5181 – 10L80/10L90 Car Transmission Adapter – must be used with both BHS5182 and 12644HKR-1 BHS5182 – 6L80/90, 8L45/80/90, 10L80/90 Transmission Adapter – use with 12644HKR-1 BHS5183 – Tremec TKX 5-Speed Transmission Adapter – use with 12644HKR-1 *TH350 Transmissions can reuse the factory transmission crossmember, but the slot in the center of the crossmember will need to be elongated in the forward direction.