I carry the original 14" x 6" BFG space-saver spare- the second version as the first issue '71- early '72, was recalled for defects. It's only good (as I found the hard way) for about 50 miles at 50 mph max and will indeed do a number on your ZF's LSD clutches. They are really extreme-light-duty 2-ply inner tubes with a printed tread, so smooth dry pavement use only.
Next caution- some gas bottles once sold for inflating the spares, used PROPANE as the pressurized gas! Anyone ever in the military well knows that a pressurize propane bottle is a BOMB. If the warning label on your says 'Danger-Flammable', that's what you have in your trunk. They HAVE blown Pantera hood and trunk lids off from overheating. BEWARE!
The even later spares made after 1980 NOT for Panteras- the 50 psi high-pressure spare that looks like a 16" x 4" motorcycle tire- barely fits canted in the rear luggage tub. With a dropped battery and some rearranging of the clutch and brake lines, it CAN fit flat in the front trunk. I suggest bolting it down so it doesn't go through the windshield in a collision, like one did in the original '71 crash tests.
Also carry an 18" bungee cord to hold the unlatched trunk lid down, as a flat tire mounted on any Campy 7" to 10" won't fit in the tub, either. Or your passenger will have it in her lap for the ride home.... Gr-4s were required by FIA rules at the time to carry a mounted spare at LeMans (at least for Tech Inspection), so their 14"x15" wheel & tire was bolted directly on top of the ZF with a small bracket. Cobras at LeMans had to put up with the same nonsense.