Chuck, guess I'll try this. Lol
The 71-72's used D1ZZ-18813-A which is a round telescoping staff antenna. The D1ZZ service part was replaced in 11/75 by D3AZ-18813-C which is a LTD round staff telescoping antenna. The 73 Mustang used D3ZZ-18813-A which is a round staff non telescoping antenna. The D3ZZ antenna was replaced by D4AZ-A, D7AZ-A, and finally E3AZ-A which were all LTD antennas which were round staff non telescoping.
I believe a lot of confusion stems from the fact that a radio was not standard in our Mustangs. Even when a radio was ordered from Ford it was not installed at the Assembly plant. A radio kit was placed in the trunk along with wheel covers, floor mats and other loose items to be installed at the dealer when the vehicle was PDI'd.
Many dealers ordered cars with out radios so more profit producing aftermarket units could be installed. Dealers would then pull a in stock antenna off the parts shelf (Usually an LTD unit since they were considered a one size fits all) and hopefully drilled the antenna hole in the correct location. Unless the dealer had saved the template from the factory radio kit that didn't always happen.
I have heard of a few very late production 72's that had the 73 style antenna.With dealers installing these radios and known to have substituted parts,anything is possible. There is also the possibility of a D1ZZ shortage near the end of 72 production and the D3ZZ antenna could be a Ford authorized replacement in the radio kit.
It's been many, many years since I was involved in any judging, so I checked the most recent MCA rules and they do allow the 71-72 collapsible round mast or the 73 fixed round mast on 72 Mustangs.