I would love to be able to track down a Max Gray D16 one day. I am not normally a fan of most 19th century American Standards, but the ones that were built and / or rebuilt in the 20th century I find fascinating. While anachronistic, I would put a D16 next to my F3 mogul next to my postwar K4 in a heartbeat on my layout and not even concerned about the prototypical infidelity in a heartbeat.
Here is an interesting piece I picked up at York a number of years ago. It is a custom built HO GG1. The frame is rigid so I don't even want to hazard a guess on the curves it needs.