This does not use the utilitrac to mount. This extender has two brackets mounted in the opening to the bed. The utilitrac system started in 2005.blackwidow, sorry for the delayed response. Nothing much was going on here so I stopped checking in on it every day.
I don't know what you are referring to in terms of "rail system". Our Frontier and a golden colored metal bracket on each side of the tail gate. The Bed Extender has a pivot point on each side that fits in the brackets. You lift and swing it out, or lift and swing it back into place. Perhaps others will chime in.
It is still available and for sale if anyone is interested.
It should fit all the first generation beds as they are all the same width.Clint, this one is brand new from our 2004 Frontier. Do you know what other years it is compatible with? TIA.