Slant six info

The motor mounts changed to spool type in 73. Keep the ones you have on the 65 now.

The cylinder head got hardened seats in 72. Very good for unleaded fuel and DD usage.

The 904 on the /6 does not interchange with the V-8. Starter motors mount in different places.

IIRC, the 65 uses a trunion joint on the forward end of the drive shaft. If you go to a '66 or newer transmission, be sure to get a yoke and a driveshaft appropriate to the wheelbase and rear end type of your Barracuda.

Engines can go either way as far as lifters are concerned. Remember with hydraulic lifters, non-adjustable rocker arms should also be used.