904 pushbutton conversion
. As mentioned 1965 is the only year with a standard style slip yoke.
Sorry, not correct. First year for the slip yoke on the 904 trans was 1966. The 1965 904 trans had the flanged output shaft, small input shaft, and a cable shifted valve body, that was the 1965 only. However the 65 valve body can be swapped out to the 64 down VB to make it work with a PB shifter. The 65 valve body can also be modified (manual valve, rooster comb, and neutral safety switch) to make it work with the PB shifter.
Just a FYI, the 64 valve body cannot be easily modified to work with a 1965 column or floor shifter. The 65 manual valve will not fit in the 64 valve body.
My 66 Cuda had a 1965 904 trans, with a 1964 valve body, 64 PB shifter in a floor consol between the seats. It also had a 1968 V-8 front internal section, to get the larger input shaft and the larger clutch pack. Another FYI: you cannot install the low gear set in a 1965 or older 904 without major mods to the trans.