Yep there was a Cobra in 79 and 80. Had a big snake head decal on the hood, a special hood scoop, and a similar bumper cover and spoiler to the 82 gt. If anyone has an extra front spoiler, I am interested.
On the rear, I have run G50-15 MT Indy SS tires on Ten Holes, and 275-50-15 BFG Drag Radials on Ten Holes. I have 15x7 Draglites on the rear of my 79 Capri, and 15x8 Convo Pros on the BFG's now, on the 82.
On the 82 with about a half coil cut from the stock springs, I finally put an airbag in the right rear because it rubbed on track launches. Also rolled the fenders.
With air bags, I think you could use the 10 in rims. I have seen a bunch of cars with 26x10 MT ET streets, etc, on Draglites and Ten Holes.
Its close enough to try. I think 5 or 5.5 in back spacing will work. Backspacing will be very important.