5.595 - 3650632, 1 1/8"-18 fits 1939-59 and my books don't go any newer than that so they may even fit the newer ones. I would think a Chevy dealer would have them or be able to get them but maybe that's why your asking Fred???
I checked McMaster Carr and they don't carry anythng that fine, but maybe that's why your asking Fred???
Short of that I'd have to spin on up in the lathe. Might not hurt to order a couple of feet of 1 1/8" bar stock and make some up. Looks like there's a market for them. I'm supprised none of the vendors carry them. I don't have time to check Restoration Suppy in PA, right now but they might carry them.
Where'd ya find your new one Ralph??
Denny G