Actually, I think the 64-67 Muncie shifters are really good, and that's what I have in my 68 now,but in 68, GM dropped the reverse lockout and began mounting the shifter to the crossmember. When the motor mounts flex, it binds the shifter, and without the reverse lockout, it's too easy to get into the reverse quadrant instead of first when downshifting. I don't like the sound that makes....but I am wanting to get the original shifter back in.
Yeah, I know that I shoudn't, but I will make some hard shifts sometimes. I once broke the handle at the 5/16" threads for the knob on a 68-up Muncie shifter - I can't help it- it's the same reason I haven't owned a motorcycle in 20 years.....but thanks for the tips and that 64-67 adapter is really cool!!