Did you ever try to convert an 054 car to 036?

The wheels themselves are not normally the issue. Truck and coupler swing and how much the body over hangs in the center and ends is. Removing wheels will not alter these issues. My scale K-line 'Madison' HW passenger cars will run on O-36 but over hand is rather bad and done often I bet would derail more than normal. What cars are you looking at??? Other here may have more info on specific cars and what track they will or will not run on well.

I've experimented some with cars and locos.  Like AMCDave says, its not just wheels, etc.  Many times its couplings and such.  Sometimes just removing a ladder or body part that prevents a coupling from sliding to a great angle will "fix" the problem of tighter curves.  sometimes it take s more work. 

I've modified several locos so they work on tighter radii.  Sometimes the trucks will fit on the tight curve rails but not turn enough on the body to make the turn - you have to take apart the loco and modify it so they will.  The most dramatic being the RMT BANG, which with a bit of work on coupler and opening up the pivot angle of the trucks (will run on 'Streets curves.

Generally, I've found that six wheel (three axle) truckson big diesels and passenger cars are more limited than two wheel trucks (no surprise, really).  They do have a limit on how sharp a curve they will take regardless.  Some meant for 54 will not go below about 42 even if you modify them to pivot to a wider angle - the three axles just will not cleanly fit on a tight curve.