The beige 201K23 is a bit different is some ways, mine takes an inbetween motor belt size to any of the black 201s (small and large hand wheel). I know very few came with the spoked hand wheel for hand crank and treadling. The castings of the aluminium body is not the same as the cast iron version, and it's possibly so with the hand wheel. By the mid 1950s most machines sold were setup with motor and lights by far (there isn't much detailed info on these), I have seen a single aluminium bodied 201 hand crank with all original parts. From the web I have seen some use a black, spoked, cast iron hand wheel from an older machine, but I don't know if it needed alterations for the aluminium body to accept it.
A model 66 is a nice machine, much the same drop in bobbin case, occilating of course. Cleaned and well oiled it's a smooth machine capable of exactly the same as a 201. The 201 runs a bit smoother, three sets of meshing gears makes a difference, but in strenght and capability they are equal. The 201 has a full rotary hook and race, and a revers lever. If it was me, I would keep the 66 in the treadle, and have an additonal 201K23 with motor and lights. The hand wheel on the 66 needs oil, when the stop motion screw is off, it's easier to get oil all the way along the axle there; it's very hard to reach this part from the oil points and it's sometimes stuck. Oil and wiggeling should loosen it; and I imagine other parts of the machine might need some extra attention too. It can take several days of cleaning, repeated application of oil, running the machine and more oil to get it right again.