99+ GT's have a 16" spare. Unsure if that's the year spread, but my '03 GT has a 16" spare. I have read that it will fit the 13" setup with a small spacer.
Been meaning to test this out because I have 13" brakes on my '03 and hate doing the rear tire swap. However, i don't want to scratch up my painted calipers if it hits
On my fox, i have a 15" V6 spare. It will fit the rear Cobra setup, so i just swap the rear tire to the front. However i hink i'm gonna go 275's in the rear on the fox so i guess iwill either need to get a 17" spare, or figure out if the 16" GT spare will fit with a spacer