early a engine swap

Hard to believe you can't find a good slant cheap in the LA area. In addition to tranny, you would also need a V-8 steering center-link and a 64-66 small block oil pan (or dent in a late pan).

If you go V-8, I have a 65 small block 727 push-button tranny I will probably never use, and we are driving to San Diego in a few weeks. I am not sure the cable-shift pattern is the same as 64, since 65 changed to the now-standard P-R-N-D-2-1 pattern. It might work, but you might need to re-label your buttons. You also must beat the body crimp up to fit the 727, but otherwise is the same. PM me if interested.