Wiring harness for rear?

[Broken_down?]

Ok I am looking at buying the rear wiring harness for my 68 chevy pickup 2wd LWB Custom Camper. it is a 50th if that makes any difference. here is where I am looking to buy from as of right now.

http://gmcpauls.com/wireharness2.htm
item: http://gmcpauls.com/pictures/WIRE/Brake%20&%20Backup%20Lamp%20Harness%20(Pickup).jpg

I looked at the vin decoder on site and it says my truck is fleetside. is this correct? Does the pickup with stock wiring in it currently have this plug near the cross member? this would allow me to replace the wiring from crossmember back.

Thanks
Rich