The 2.2 pistons have the same wrist pin size as the SL6. (.901)
You do need to check clearances base on the exact 2.2 piston you end-up with because some are slightly smaller for a "floating" pin.
This is the main reason this "long rod" swap is so popular, it all "bolts together" with-out any special machining and there are a number of different 2.2 pistions styles to choose from, ranging from a large dish turbo piston, a mid-size dish & even a flat top piston... basically you can get compression numbers between 7.5 to 11 to 1 when swapping them into a SL6... just by doing the math and careful piston selection.
There are a lot of the 2.2 family (87.5 mm thru 89 mm) pistons still in distribution but most of the forged ones have "dried-up".
(TRW / FM / Sealed Power list old P/Ns)
As for the Corvair piston, it works... I have used those but availability is limited these days. (no off-the-shelf forged pistons anymore)
These pistons use the Chebby .927 wrist pin size so a SL6 con rod will need to be reworked to fit.
One more thing, those Covair pistons start at 3.500 bore and they have a pretty slender "slipper skirt"... so when using these pistons in a high HP SL6, I have had the same broken piston skirt "illness" that many GM hot rodders seem to get.
DD
