I have a 65 Barracuda with a slant 6 - three on the tree want some transmission/engine advice

Here's a 904 transmission and all the kickdown linkage, but shipping may make it a no go, as it's on the other side of the country from you.
https://www.forabodiesonly.com/mopar/threads/1967-225-slant-six-and-904-transmission-200.547684/