Question on 86 Fleetside Short Bed Box

[11555wally]

I looked at a short bed fleetside box today that was said to be 79-87. It looked very much like my 86 with a couple of unexplained differences. The main thing is that the floor of my bed is all one piece. The one I looked at today had one large piece and then a small piece in front of the wheel well and one piece at the rear of the wheel well. It looked like it was original with seam sealer at the joint. The other minor point was some sort of a sheet metal guard near the opening for the gas filler tube. Could this have been an earlier/later model. Everything else looked the same as I could remember mine looking like. Appreciate some comments on this. Thanks