Mountain drive (mine) is a Reduction gear (130-54) the Speed drive 110 is an overdrive 34-'54',

but the frame BB edges must be Chamfered That is where the torque transfer is..
and So you need the shop tool facing cutter.
.(in France shopt that used to set Up Mavic equipped bikes needed one for that company's BB installations)

The Mk4 BB edges are somewhat faced with a Bit of a Taper , just not enough for the needed grip of the SD installation.

because of the Torque transfer needing to be More solid, the B version MD has a Knob sitting on top of the Frame
behind the BB where the rear Fold Pivot is, .. on the end of a Lever .
so It turned out to be more User Installable . on my Mk 3 & moved to My Mk4.

[if you got the version for other bikes that torque arm has a bolt hole and you wrap a coaster Brake type strap around the right chainstay. ]

Of course the big difference between a derailleur and an Internal gear is shifting, you cannot push a chain off a sprocket while you are stopped .




'/,