Stan,
The threaded jiffy stand is a neat idea. But considering the use (and abuse) jiffy stands get, I wonder if such a setup would have result in the bolt either getting jammed and never coming out, or coming loose at inopportune moments - like when riding down the road.
The 1953 Spare Parts Catalog (Oct 1952) calls it a pin, and shows a pin in the illustration. Lousy illustration? Below that, in the footpegs, the shoulder bolts are drawn accurately. I suspect that if it had threads and a hex head, Harley would have called it a (machine) screw or bolt.
The 1954 SPC (June 1954) shows a -52A jiffy stand leg, replacing the -52 and used on 1952-1954. I always assumed the 52A had a different bend to match the different front-end geometry, but that could be wrong. The 1954 SPC also shows both the -52 pin (used on 1952-1953) and the -53 pin (used on 1954). But 1954 was such a screwy year - some changes didn't happen until near the end of the year, but the book doesn't say that.
Perhaps the two pins have a slightly different diameter or length. Does anyone have a collection of them and a micrometer? Who's got a pretty original 1952 or 1953 bike? And a later one to compare legs and pins?