big boys n 063

It will run on FT 060.  It will also make it through an FT 060 crossover but you need to leave the deck plate down or it will bind on the tender.  Generally it does not look particularly graceful on 060 curves but, as you said, it will allow you to get it into your yard.

I'm sure if you pop a couple axles out of the tender it'll do O54.  I put each piece on Atlas O54 and hand pushed it.  The locomotive fit, but the tender did not.  The locomotive didn't fit FasTrack O48.

Now my MTH PS-1 equipped PRR T-1 did take O48 curves (It's also rated O72.), but it was working hard to get through them.  In fact I've only had one locomotive not take tighter curves then it's rated for, and that is my K-Line GG1.  I believe it's rated O31 (Have never found a spec for it.), but it won't do O27 and I'm not even sure it'll do O31 as O36 is the next size I have.