P/N - B7AZ-1705-A - 1 1/4 inch long - MPC 75 ed, sec 10 pg 60
P/N - C0DZ-1705-A - 7/8 inch long - MPC 75 ed, sec 10 pg 60
P/N - C6AA-1705-D2 - 1 1/4 inch long - Mustang Monthly, Sept 2005 pg 52, picture (smooth base vs grooved base)
The manufacturer was Dill, and their name appeared on the tip. Their base was grooved, at least on the samples I have.
I don't see how any determination of correct length can be made based on what is currently known, for both original factory equipment and current NOS availability. The MPC lists two different lengths. The MPC is also the source for service replacements, it's what Ford determined what would fit and could be used as a common replacement. The manufacturer of those MPC replacement was not indicated.
The criteria used in MCA judging is the extension should be present on Mustangs with wheel covers, and more likely than not, should have a visible silver pressure stop. Length is difficult to determine without disassembly.