Reply to "replacement rear calipers"

Tony, with the scarcity of Panteras in your area to compare, be aware that most early (pre-'80) Panteras had 0.810-inch thick solid rotors. The exceptions were the rare Gr-3 and Gr-4 racecars that had thicker 1.25-inch thick vented rotors. So calipers made for one rotor thickness will not always fit the other, even with spacers as shown between the caliper halves on the SVA website. Some spacers can be added or removed, but its an individual thing from each mfgr.
Stock Girling iron 3-piston calipers used on post-'80s Panteras are monobloc types that are not split, so no spacers can be added or removed; on these rear calipers, the cable operated handbrake caliper was a 'pair-of-pliers' type also used on some Rolls-Royces. This is quite different from the sliding 1-piston Girling rear caliper- stock for your year of machine, with a handbrake that was integral to the caliper and cannot accept a spacer for wider rotors.
Finally, it's possible to add a separate cable operated Wilwood handbrake caliper to each rear rotor, with its bracket. At least one U.S Pantera vendor sells such a system for completely stock Pantera cables, or if you have fabrication capabilities, you can make your own bracket. I did this some 15 years ago and its worked well; it will pass your MOT.
Bottom line: adapting calipers, rotors and handbrakes is not a trivial exercise, so stay tuned to this Forum when you decide what you want to do with your car. We can tell you what fits (usually) and what doesn't except at huge trouble & expense.