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.
[URL]https://www.forabodiesonly.com...25-slant-six-and-904-transmission-200.547684/[/URL]
Bingo, even if you can’t make that deal work, someone else will have a pre-‘68 slant six 904 closer to you, and it will usually be very affordable.

If that person is doing a V8 swap, they most likely wont need the driveshaft either. I think you could easily do the whole 904 conversion for under $600 if you are patient, and buy used parts.