Who's running the same size tires front and rear

Staggered width but same or close enough to the same height/diameter to use one spare for the front or rear.
245/45-17x8 (25.68") front 275/40-17x9 (25.66) rear on my 'Cuda

Running the same 275/40-17 on the rear of the 69 Barracuda and the fronts will be something very close to the same diameter... like 245/45-17 (25.68") or 215/50-17 (25.46" diameter). Fronts are still TBD.
Close enough to a 135/80-17 (25.5") Temporary Spare diameter for me. That's what will be in the trunk of the Barracuda. It fits the tire well easy and lays below the trunk floor, so I can place a thin board in the trunk to cover the spare and it will lay flat. Will be upholstering or carpeting the trunk to look more like a new car trunk.