A904 slant 6 1968 and after transmission

Things to consider....First, check your crank. The '67 and earlier slant 6 cranks use a small converter register. '68 and later use the larger register. Internal spline differences changed then too. Next check your neutral safety switch. Early '68 uses a single wire neutral safety switch. Late '68 and newer use the 3 wire switch. Swapping these parts require other modifications. As mentioned, forget the 727. It would be hard to find, would need other mods, and is totally unnecessary for most applications.