The TPMS has been in 150's since the 07 model year. There is no way to turn off or disable the system, it is federally mandated that it be there, so ford is not going to allow for a way to turn it off.
You do have a few options,
1. remove bulb from warning light
2. cover light with black tape
3. put your stock wheels back on or pull your sensors out of your old wheels and have them installed in your new ones.
Back in early 07, some one tried putting the sensors in a pvc pipe and sealed it up and put 35 psi of air pressure in it, thinking it would trick the system. It does and doesn't work. It was fine as long as the truck wasn't moving, once he started rolling, the system knew the sensors were not in the tires anymore, so the warning light came back on.
I've seen it suggested that you could swap in a pre 07 guage cluster, cause they don't have the TPMS light in it. I don't know if it will work or not, but the odds of finding a 3 year old or older cluster with the same low mileage that your 08 has are slim to none.