I think my tranny is toast.

I had a similar problem. The P.O. had put a shiftkit in mine, similar to a slapstick in an Ebody. The linkage was all wrong. If using manual you could make your way from first up to drive, and push it into neutral (not good).

I messed with the shifter linkage a bit, and corrected that, locks at drive. Works a treat now. Glad you got it sorted out.