I went through this a few years ago and created a spread sheet from the parts books. From 59-69 the coil and armature had the same part number. Solenoid was different and heavy duty for the hemi. Most of the internal parts are common. In 66 whether slant 6 or hemi you had the same clutch/gear. Barrels had some different part numbers and probably a common one for rebuild. In the end, the nose piece is what distinguishes how the starter orients and mounts. The Slant 6 will not work. Places starter solenoid in the wrong position. 66 nose was different than 67 up because the hemi flywheel had a different ring gear location in 66, though it is a minor change and folks say either started works.