Dave,
The Fort Worth AT-21 remains were saved by the fellow WIXER Dan K. mentions, Craig Cantwell. To go back some there was a 2-photo (front and rear views) contribution made by Rick Matthews to the February 1981 (Vol. 17, No.2) Air Classics Warbird Report showing the remains in the weeds at Forth Worth. Sometime later (I don’t know the dates from this scanned photocopy below) another two photos sent in by Rick show it being loaded up and moved.

Craig’s example is extra rare in that it is reported be serial 42-48053, the second of just 39 built by Bellanca, of a total 175 AT-21 variants (30 built by McDonnell).
Interesting that the AT-9 story comes to light here. The Spartan School of Aeronautics in Tulsa, had at least one AT-21 as late as 1953 and at least a couple of AT-9s. See this FlyPast thread:
http://forum.keypublishing.com/showthread.php?t=41284 I have made the AT-21s a personal study over the years but this was news to me about the Ponca City, OK fleet! My dad had ferried two AT-21s after the war though it is unclear to me (and I forgot to get specifics before his passing in 2004) from what Surplus Field to just where he went with those. He had ferried some other aircraft from Kingman to Prescott on short hops because the fuel was much cheaper at Prescott where he lived, and new owners would buy just enough at Kingman and then top off at Prescott. I am not sure if Kingman had AT-21s though? Ontario did. I have one photo of one of them with my dad. It seems like a match to the one at Spartan in Tulsa that Dick Phillips posted in the FlyPast thread. Of course once de-militarized (turrets, markings) and left painted overall silver they would all look the same.

I don’t yet have an AT-21 documented with a registration beginning with “67xxx” The known AT-21 registrations I have include: NX25663; NX33690; NX63342; XA-FUI; maybe XB-XYZ (said to be a Bellanca ship). William Larkins said there were ten on the U.S. Civil Aircraft Register in July 1949. Warbirdnerd’s post above shows us the Larkins photo of NX63432.
I thought of something after posting here that I should expound on. My dad flew charter flights for S.E.P.C.O, (I believe headquartered in Phoenix) during much of 1946 and some of 1947. The charter flights the company did with my dad were a bit mysterious in several ways. Usually his customer was usually a Mr. E.G. Miller and they would fly to many locations in the western United States, at some odd hours and meeting with some big names of the day. Miller requested no log book be kept. My dad secretly kept one anyway, and it of course included his other flying of those days. One day he got caught by Miller making an entry and the log was taken and destroyed. I am thus without several months of history of my dad's early flying days and this includes the AT-21 flights. I don't know that SEPCO had involvement with the the AT-21s or not.
Lowell