Thanks, lovin the seats- and even heated to boot!! Big hit with wifey;-) It was totally custom, and we ended up mounting them on the slider frames that were there originally. Consequently, the travel for and aft is now double!! Sadly I do not recall the exact vehicle they came out of, but it was late model GM, from Ebay. Hope this helps, as this was probably the biggest improvement on the truck.
Also, just fitted new OEM shocks, so the ride is sweet. Now to install the steering upgrade...