I have found that quite a few of the bigger scale articulated Lionels that are rated for 072 minimum; will actually navigate 054 quite reliably. And several that are rated for 054 will actually operate on 042. One notable exception is the articulated EM-1. It will not handle anything less than 072, because the rear power truck is firmly affixed to the frame; ie it does not swivel. Same with the UP 4-12-2 3 cylinder, and the VL Bigboy.
Rod