03' silverado max tire size questions

I have a 2003 silverado Z71 and would like to put bigger tires on it to raise it a LITTLE bit with out having to pay out the tail for a lift. Does any one know what the max tire size I can put on the truck with adjusting the torsion bars and not having them rub anywhere?

i had 285/75/16 on my 2000 with torsion bars raised and i had no rub. they said i would be able to get 295/75/16 under there too? but i know 285 will fit.