another picture.

I measured again, and while the OD is ~4.200" at the top of the piston, it measures ~4.245" across the bottom of the skirts. I checked a few, they are all similarly tapered.. I didn't realize they had that much taper.

If anyone could find a listing for a 2406648 anywhere, I'd be very grateful. At this point I am thinking it's an 11:1 426 piston.