John,
let me look around - I may have some info on a U-75, though it's a little later, and bigger, than I'm accustomed to dealing with. Stay tuned . . .
The ball valves are adjustable, I think - it has to do with disassembling it, and adjusting the seat inside by screwing it in - or out - to tighten up the seal. New gaskets do wonders with keeping the couplings from leaking, as well.
What's the serial # on your truck, and where did it serve? I have a buddy who's keeping track of all the American trucks . . .
-Michael
