I believe the original poster asked about O-27, Not O-31. Most of those engines mentioned in the previous post will not operate on O-27.
Some others that will operate on O-27: the Lionel General 4-4-0, the MPC era GE U-boat, any of the single motor Lionel F-3's, the Lionel 1666 2-6-2, and the various Lionel Vulcan style switchers.