Re: Spare tire?
Check out the thread at the link below for discussion of this same question. I don't know what size tire you are plannng to use, but I have 17" wheels and carry a 225-60-15 spare tire on a 15" wheel that matches the diameter of my rear tires (didn't want to have to buy another 17" wheel and tire). If you are running a posi then matching the tire diameter on both sides on the rear is necessary. If you are running aftermarket front brake calipers the 15" wheel probably won't fit. The GTO wheel/tire/spare may work too, but I'd want to make sure I didn't have a difference in overall diameter across the rear wheels with a spare on one side. You may also need to carry different lug nuts (and wrench) to fit the spare than you use to mount your 17" wheels.
'69 Z/28, Lemans Blue/White Stripes, DZ302, Tremec Magnum, 4.10, Procar Elite Seats,
Custom Upholstery, Dynatech headers, 17" VWW V45's, 235/45, 275/40, C5 Front Brakes