Another 51 here. Mine is a C1 that I bought from Steve Azola 23 years ago, doesn't even have a Kay brand on it, probably was an OEM for Sears. Since then I've had a new bridge made for it and the fingerboard planed and painted, yes painted, once. It makes a big boom and rattles windows with my current 6 year old set of gut strings on it. I've oiled those once and lightly sanded some hair off of the G string maybe twice. They stay in tune almost as well as the Evahs on my carved bass.
Not saying that people don't have problems with gut strings, just that I never have.
But if I were in the market for a ply bass now for BG, i would be looking around for an Engel. They are basically the same, and I see those with what looks like a good setup for under $1K. Get an Engelhardt, put a Kay emblem on the tailpiece, and everyone will be satisfied.
This guy, Kyle Perkins, fixes and sells american plywood basses and has a house full of them at any time. He has American Standards, Kays (many Swingmasters, etc...), King Moretones, Engels, Gibsons, everything. But guess what he plays?