I'm glad this is my hobby, and not a business for me ...
Despite my research, just figured out that the rings I ordered and the three surviving pistons don't match. Beware!
Apparently there was a redesign of the SPI pistons, changing from a 1.2 mm top ring to 1.5 mm later. The ring set should have fit, from my research on the replacement piston I needed (with the C-shaped valve groove on top). But no ... my original pistons are of the first generation.
So, after some mental gymnastics and consternation, decided to buy a whole new set of pistons (now on order, along with the new fan control relay) instead of the expensive 1st gen ring set. This will yield four matching pistons and rings, instead of mixed. The wrist pins are pressed into the connecting rods -- my hydraulic press awaits.
I have plenty of other work on the engine parts (cleaning, etc.) and car to keep me busy 'till the pistons arrive.
I'll post my spare old (3) and new pistons and wrist pins, and one spare set (for one piston only) of new 2nd gen rings for sale, along with any other leftover parts, in the Buy/Sale/Trade Parts/Accessory section of the site when I'm done with the restoration of the car. Search for a post there by member "LugNut" in the not too distant future.
I tried to post another parts-wanted there this morning (I need the OEM 5-speed+R pattern shifter insert (goes in the top of the factory knob)), but it wouldn't let me post. Somehow I slipped a WTB post through there before, before my 30 days' new-member jail term is up?
BTW, the new LuK clutch set looks excellent, and is the same as what was installed but the original has both LuK and Ford marks. Clutch set is from the UK.