Hi Harold. I also wondered if the car might be a '52, but the VIN fits within the range of id. numbers from the 51's built in L.A. Also, I read an article which listed some differences between the '51 and '52, such as for the '51 the name Plymouth on the glove box door vs. no name for the '52, and the hand brake handle in chrome for the '51 vs. plastic for the '52. All these things indicate that my car is in fact a '51. Perhaps, as you say, over the years someone retrofitted the car with the overdrive. Right now the car is at my mechanic's, but when I get it back I'll do some more checking. Thanks for offering to be a resource. No doubt I'll take you up on it. Feel free to contact me directly at jim108@comcast.net.