W40/50 share the same bellhousing
W57/58 share the same bellhousing
w40/50 bell/h is not compatible with w57/58
They are the same length, thus no tailshaft mods
The Xmember position is approximately the same (few mm from memory) so doesnt require any xmember mods
W40/50 shifter positions are interchangeable
W57/58 shifter positions are interchangeable
w40/50 shfiter is not compatible with w57/58
Shifter positions are available almost anywhere for both boxes, depending on which car they came from.