What Bob said!
" I believe the locomotive could do O-54 curves but the passenger cars needed O-72 due to the method of articulation."
I have run the locomotive and tender on Super O modified by Rich Riley to 054. It will run on 054 with no problem with the exception of the tinplate wheels on the tender (whose flanges are too deep). Not a problem for most people as there are relatively few of us who run Super O.
The passenger cars will not navigate the 054 curves without modification. I modified a tired M10,000 set a few years ago to run on 054-it required removing some material from the floor casting for the rear truck in the observation car to allow the truck to swivel far enough. The sheet metal "tongues" that engage the vestibules on the passenger cars could be moved away from the car body a bit by loosening the screws-this allowed them to (barely) negotiate the 054 curves. As I recall, the special front end on the car closest to the locomotive on the Hiawatha would require some work in order for it to swivel enough. So far, I have opted not to modify the Hiawatha as it was NIB-this may change in the future.
MALLARD4468's comments on the bubbling issues are accurate. The set I picked up last year has bubbling under the paint on at lease one of the cars (it was inexpensive enough that I went ahead and purchased it anyway).
M10,000 running on 054:
It still slows down a bit on the curves, as is evident in the video.
