Tire Pressure Indicator Check / Info

[Guest mudddvayne]

I recently purchased a 2007 GMC Sierra 2500HD. It has about a 6" lift on it with aftermarket 20" wheels and 325/60R20 Open Country tires. My questions is this... On the dash, a message appears that says to check front left tire pressure, front right tire pressure and rear left tire pressure. Since the truck doesn't have the stock wheels and tires on them, does the truck still monitor tire pressures? Also, the stock pressure settings as stated in the truck's door jam says front tires need inflated to 50psi and rear tires 80psi, however on the tires themselves it says put tire pressure at 50psi. What should I do? Is there a way to disable messaging center about checking tire pressure if there are no sensors in the aftermarket tires/wheels? I don't even know what to look for on the wheel itself as to what is the sensor for tire pressure and how does it work?