K&D refers to the motor manufacturer - I have forgotten, but I think
Kendricks and Davis? Lobaugh put their own labels on them after a while.
Sprung drivers are a "thing" in 2-rail. The axle has little bearings that ride in a slot, and move up and down with typically a coil spring pressing downward. The technical terms are "
Pedestal" which is the slot itself,
"Pedestal Binder" - the little keeper that holds the bottom of the slot together, and
"Driving Box" - the axle bearing. The
Church and Kratville books are great references.
Pete mentioned the B&A - the Lobaugh is most accurate as a CNW or THB - the MoPac and IGN are relatively easy. The Superpower versions are not quite as accurate, but close enough for guys like me. There were two versions of the B&M, and of course the B&A versions and the original Lima #1, which are slightly different. Let me entertain you with the one the SP purchased from B&M, and subsequently modified. There are no known photos of the prototype showing a retained Walschaerts gear after feed water and tender mods, but there is also nothing that indicates it isn't true to a prototype.
The most serious flaw is the length of the smokebox, which I am sure you, and definitely I, can overlook:

I specialize in these tenders. You cannot see it, but I simulated a welded seam about a scale foot up from the bottom. This is a 120 SC - converted from a 90 SC, originally supplied with Mallet Moguls and Mallet Consolidations. Also note the sand dome, which is not correct for the SP version, since it was supplied with the group with six axle tenders - at least one wound up on the Santa Fe. Next photo will show that corrected.