I took apart 1965 D100 and 1968 D200 slant 6 to get parts for my 1967 W200 (Small block V8). In both slant 6 engines, the bell housing curved beyond the slant 6 mounting surface with exposed bolt holes, so it could be used with the small block V8. The W200 did have the NP 435, shifter on the floor. Both slant 6 trucks had 3-speed shift on column. I remember all 3 bellhousings being the same. I had thought the flywheels were universal because the bellhousings were the same and the small block 318 and the slant 6 were both internally balanced. I remember the starters also being the same. If I'm wrong, OK.