Yes, 210F75, 250P75, and 180P75 long-distance tenders were used behind K4's.
The lone 180P75 was used behind streamlined K4 #3768, and was later destreamlined and converted back to its freight appearance as a 180F82, where it spent the rest of its life behind the I1s that somebody around here made a model of many years ago.
John, your conversion looks great. A K4 with a long tender is a pretty engine.
