GM-Aluminum 621-Bellhousing to SB/BB GM# 3899621/ 4-speed bolt pattern



Aluminum bellhousing for direct bolt up to Muncie 4-speed bolt pattern

(GM TKO500/600) behind GM small block and big block.
GM621 bell
No adapters are required.

(Does not come with fork Pivot)

Pivot stud  please see item#  MD-401-6026
    Reproduction of the GM# 3899621 bell.


These cast aluminum bellhousings connect Chevy small block & big block, engines to transmissions utilizing the standard GM pattern such as the Muncie, Saginaw, Borg Warner T10, and Tremec TKX or TKO transmissions. The bellhousings are designed for both GM cars and trucks and other manufacturers where swap applications are being installed.


  • Factory-like attachment using a stock or Holley oil pan
  • Lightweight cast aluminum design 
  • Lower cost non-SFI rated option for projects that do not require a steel SFI rated unit
  • Designed For Hydraulic and Mechanical Fork Throwout Bearing Linkage
  • No hardware included
    For mounting hardware please see 


Additional information

Weight 144 oz
Dimensions 17 × 17 × 8 in


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