RE: Common parts TD vs. Medallions
The prop drivers are dimensionally the same-but the TD one is anodised gold-and should have a thin steel or fibre shim washer behind the prop driver-both the anodising and the shim washer are absent in the Medallion. The plastic carb housings (I refer to them as such-because calling them 'throttle body' is incorrect-the throttle body would be the part that contains the rotor, throttle arm and NVA in the TD 05 R/C-and as such is available as a spare in its own right from Cox Int'l) are interchangeable-but the respective NVAs are quite different-so those parts would have to accompany any swap. As you surmised-the backplates too are interchangeable.
There are not too many parts from each that are common-ie the same identical component is used in each engine-only the case, collet, the prop screw/spinner and backplate-(OK if you want to be really picky.....the head gasket!)-but virtually all parts are interchangeable. Not all will have an effect positive or negative on performance though, if interchanged.............the parts with the biggest effect are the piston/liner set, the crankshaft, and the glowhead-and these three are completely different between the two variants.
ChrisM
'ffkiwi'