I put a Rennshift in my '72 tailshifter. In concert with a little sweetening of the mechanical fits at the steel ball on the end of the shift rod and the inside actuating lever the shifting is great. That gear-bag feeling on downshifting is completely gone and the upshifts are nice and positive.
I really couldn't be happier cause now I've avoided doing the whole tranny, linkage, motor mounts swap to get decent shifting!
Now the side shift tranny I've got in my garage will become a parts tranny when I need it later. Or maybe I'll just sell the whole thing and buy something more fun to play with...
Have fun,
Kevin