Chassis donor: untouched Wms/Samhongsa Southern Rwy Ps-4 from 1980's. I used this chassis because it has Walschaerts valve gear, which the K-5 had.
Boiler donor(s). Found beaten-up and pretty cheap Sunset K-5 boiler on eBay years ago; then spotted the nice one not too long afterwards. Sigh. Couldn't help it.
Tender donor. MTH RK from USRA 2-8-8-2, but these tenders are 1:48 dimensions and greatly favor some tenders later used on the K-5's. I would post the prototype photos, but they are not mine, so I can't. The K-5's had many different types of tenders over the years, and some were a particularly boxy type, favoring these. Close as I could come in a 12-wheel.
I have already re-trucked it here, using Williams 700E-clone trucks from their later die-cast scale J1e.
Boiler work. Original Wms 4-6-2 shell at rear. I did all the exploration changes on the beaten-up buck, then, after it fit, I just copied my changes on to the nice one and, lo! It dropped right on.
Finished except for the obvious - and the headlight! The Pilot is a Lionel Hudson pilot with one pump removed, as most K-5's had only one pump (the Mercury versions had 2 pumps)
And that's it. ERR Cruise Commander and RS; Electrocoupler. I used older lettering and a number prior to the general re-numbering of 1936 (I think it was).