While my Big-Tailed Beast (i.e., a 1960 Fury) is not quite within the purview of this particular forum, it may well be a pilot car or a "mule." It is a 2-dr H/T with the SonoRamic Commando cross-ram engine. What makes it rather unusual is that it has some different features than most ram cars, most notably the carb linkage being the early ball-joint type and the lack of removable panels in the fender wells to facilitate plug changing. In addition, the swivel seats are the the earlier 1959 model types and not the automatic '60 version. What's more, while it does have these features, it wasn't shipped until 10-25-59 from the St. Louis plant and not sold until 02-23-60 (by a Denver dealer), which is a long time for a high-performance car to sit on a lot.
I've discussed this with Darrell Davis (a former Chrysler exec, Chrysler Historical Society board member, and '60 Plymouth aficionado) and we kinda have come to the conclusion it may well have been one. He did work for Chrysler, in the Plymouth division, then and he thinks it may well have been a mule and rather than shipped the dealer for sale, used by a factory rep which was a common practice then.
At any rate, while I have the build record and the sales invoice, but not any other info on the car.