If you want the extra strength of a C6 trans, this is the adapter kit to use. The modifications are a bit more extensive than for the C4, but for heavy duty use this trans is a better choice. You must have a 4WD C6 trans with a 31 spline output shaft. The shaft will have to be shortened. If you have a 66-68 Bronco, you will have to replace the front driveshaft with the later style, #3811 and #3813 Companion Flange. If you have a 73-77 Bronco with the J-Pattern transfer case shifter, the mounting assembly and possibly the shift rails will have to be modified or replaced with our #2150 J-Pattern Transfer Case Shifter to reduce the modifications. You will also need an automatic shifter. This kit includes a new extension housing, a new 31 spline spud shaft, bearing retainer and necessary gaskets, seals and hardware. Note: Transfer case will be 2.5” farther back.