So after some offtopic adventures into head gasket/stud land... back on topic.
The pistons I think are the best fit are Manley 615000C-4*, square dish (should provide valve reliefs) with 32.639mm pin height. It seems any square non-stroker ej20 piston that has the ~32.64mm pin height could be "close enough" by my redneck math. I have a set on order, I will confirm my numbers and physically check that the valves clear at piston TDC before proceeding.
CAUTION: as Quidam found on page 1, a EJ20 piston without a dish or proper valve reliefs and/or higher pin height will result in a interference motor and or piston/deck impact. The 615000C-4 pistons may still need some valve reliefs near the edges.
The easier option would be to buy the high compression flat top piston from RAM and use other methods to reduce the compression. I may just buy a set for the second motor and run e85.. If the MLS HG's hold on the first motor...
My plan for the wirst pin bore was custom rods.. But I am having trouble finding a rod maker than will make low quantities without selling my soul. In the meantime, I am going to try to rebush the stock rods with 23mm Manley replacement bushing (to match the pins). It will probably require a drill press, some beer, a 12 ton press, more beer, and a back brace for standing up for so long.
In case anyone wants to know.. the closest off the shelf forged rod to us would be a fiat abarth or a hayabusa lol but neither bore or width is correct.. ea82t: 117mm BB 48MM SB 21MM WIDE 19.4mm (or 23MM small bore if you go ej20 pistons).
(stroke duhvided by 2) + rod length + pin height +/- deck clearance = deck height
33.5 + ~117 + ~33 + 0 = ~183.5mm
ej20 32.639mm CH piston:
33.5 + ~117 + 32.639 + .361 = ~183.5mm
Note: DH might be closer to 183.65-184mm but I am not sure how decked my test block is. I'll have a unmolested block in the house to measure in a few days.
I would like to add a disclaimer to this: I would feel really bad if anyone took my advice and blew up their motor. Wait for me to confirm with the parts in hand, or hell.. don't ever take my advice. Use your eyes, your hands, and your tools (proper mics/gauges/calipers) to confirm everything..
More pictures incoming when the HG's and parts arrive..