I did mine on the '72 , it was a muncie 4 speed, but got changed to an automatic, for the cheap overdrive some 20 years ago, as stick trans even at 5 speed were running some 4+ grand at the time....
I cut the cross support about 4" from the frame rails, and while at it, I opened up the loops where the pipes ran through.....2" angle iron welded to the top/rear of the center section to overlap the pieces welded in place, drilled a hole going fore/aft through the top section to bolt it in place using the 2" iron to rest on the ends, and there is a smaller section of angle on the bottom to keep it all in line, that 1/2 inch bolt not going anywhere.....
when opening the loops, the thing gets really weak, duh....so I cut out the frame sections on the bottom to form a very wide upside down V and closed in the open frame sections and across the top a piece went straight across from top of frame to top of frame, then measure between the straight piece to top of old hoop, insert another piece and weld that in place, this forms a bridge like lattice work and frees up exhaust so that on my car just 6-8 bolts drops the exhaust on the ground, and the cross support is out with releasing the shifter parts, and the two 1/2" bolts near the frame rails....the trans is yours then......
this mod was done many years ago, over ten, anyway, doing well, not that it's a daily commuter......
:nuts: