Originally Posted by havi

Yep, the bigger trucks have taller frames...taller crossmembers.

I originally looked at the F2 crossmember for a later trans because I wanted the option to go back to original if a restoration was in order. The taper on the frame is where the crossmember fits, so no fore/aft adjustment is possible. However, the wider "flat" should make it easier. I included a pic of someone using a 4x4 sq. tube for theirs on an F1. However that was with a T5 (I think). The T18/19/Np435 has a wider "flat" for a mount and probably won't clear the half-round of the F1. I had mine all set in place, the height was close, but some "shaving" may have been needed. The bolt holes may have to be re-drilled. Looking back on it, I wish I finished it that way, so I would know for sure. I'm looking at another frame coming, and may try it again....yes, a darkside candidate is coming.