Here's a not-so-pleasant tag-on ending:
I sent back the valve that Chevy Duty sent and ordered another from Jim Carter, after talking to the sales rep about the 90° hose that I absolutely MUST have to make this thing work. He went so far as to pull the package and verify that it does in fact contact the 90° hose as they specify (not once but twice!) in their catalog.
Valve shows up, sure enough, no 90° hose. It is identical to the one Chevy Duty sent in spite of their assurances I'd get the correct hose to attach the valve to the core.
I went to the flaps and spent about $20 to get a too-big 90° hose, some clamps, and a 5/8" - to - 3/4" hose adapter. I cut down the hose to make it work, cussing the repro supply houses, and now have a working valve.
Incidentally, the Jim Carter catalog shows they sell that hose for ~$9, less clamps and shipping. Apparently it is NOT part of their valve package, only that 2" long stub of 5/8" hose.
Bill