Love your video's Steve. Oh that K4 is worth saving for sure. The hard parts your missing are all the side rods and valve gear. Those Lobaugh drivers might work if the diameter is ok. I think the SC engines use 3/16ths axles (0.1875"). I keep a watch out for driver castings over hear and buy em when I see em if they are cheap enough.
This little ugly fellow showed up on my doorstep a week or so ago in not much better shape that yours. Maybe just that it has drivers and half its siderods lol.
Bob T., This picture shows what I am missing on this loco, The left side main rod, cross head and what ever else. Basically everything but the side rod. I'll shoot you an email.