Overdrive source

[ATWEDITOR@aol.com]

All this talk of overdrives is getting me excited, thinking about the happy
and comfortable 80mph+ cruising I used to do in my 68GT, and how my fillings
are getting loose making 70 in my 72 roadster.
Question:  Other than watching ads for parts cars and used components, does
anyone have a suggestion on a source of an OD tranny without an exchange?  And
what's an acceptable price range?

Thanks

Jay Donoghue
72B
66Mustang (which could also use a fifth gear.)