15x8 was never offered on the Tahoe, they are aftermarket/non oe to that vehicle. For the studs, you can go up to a 1/2" diameter stud. You will have to match the knurl (the splined part of the stud) to the stock parts. As I recall, the oe studs are .570" x 7/16" on the knurl, you should be able to go to the flaps and match them up by cross-referencing them in the application guide. You might need to use a duplex type nut with a 7/8" hex if the nut seats are made for the larger type nut.
