99 tahoe wheel backspacing/offset

Hi, I was wondering if anyone could tell me the factory wheel offset/backspacing for a '99 Tahoe? I am thinking of putting either putting the 20"s off the '07 Tahoe or some other rim so if anyone knows the offset of the new Tahoe rims that would be great too. I don't want the rims/tires to stick out past the wheelwells at all. Right now I have factory rims with 33's on so I'm gonna either have 33's on the 20"s or possibly 35's if I can fit them. I have the torsion bars cranked up so the 33's fit now pretty easily but the 35's would be close. Any help would be much appreciatted.