the question becomes... is it even a gze block? Not much difference between a gze and a smallport n/a block....
second... most Toyota pistons, if "toyota" isn't stamped on the skirt, will say "ART" on the underside of the piston (only way to tell stock latemodel gze pistons)
I had a set of the cheap cast ebay pistons in my 7a.... had no problem with the pistons or rings at all....
you can see where the OE shows "toyota" and the cast does not
the top of the cast looks IDENTICAL (even the little nub) to the oe pistons.