If you have the original trans., it's most likely the 904 w/ball & trunion. Either way, the 383 will require a big-block 727.the reason i suggested a 65 unit is the trans. Mount is the same & you can use the cables you have now.i had never dealt with this setup before either, learned alot the hard way.the 65-727 is a one year only deal-cable shift,slip yoke.,also, 62-66 trannys have 19-spline torque converters, not compatable with later stuff(24-spline).it might be possible to use 62-64 trans.(cable shift/park lock) & keep ball&trunion,(not sure),but it would have to be from a big-block engine and i think you would still need diff. Ball/trun. Driveshaft as your 904 and a 727 have diff. Tailshaft length. I think someone(imperial ?) makes an adapter to use later trans. (67-up) with your cables,again, not sure. Hope some of this helps you.