I'm not doubting your ability to grenade a transaxle
but what is it that makes you sure the tranny is at fault?
Just curious? I've only see a few (3 maybe 4) bad ones, all of them were from racing. Two were shot because a mounting ear(s) broke off. The rest of shifting problems can be acredited to the shift linkage. A bad sychro or worn dog teeth shouldn't stop you from driving the car for a short time.
try these:
www.pelicanparts.com/techarticles/914_tranny_repair/914_tranny_repair.htm
www.pelicanparts.com/techarticles/914_shift_improve/914_tail_shift_improve.htm
www.pelicanparts.com/techarticles/914_shift_improve/914_shift_improve.htm
If that dosen't work I have a '72 tail shifter... in Miami, sorry.