4.2 vs. 4.0 Piston Size (measurements)

[ibanezjeepguy]

just doing a size up in my block to see if rings come down too far and interfere with an imperfection in the lower cylinder wall that I'm going to try and have a machine shop grind away.

I still have the old 4.2 pistons pressed to the 4.2 rods so I bolted them up to the crank but noticed there is a lot of slap.

the pistons look almost identical from top the bottom even the pin height looks to be the same but the diameter must be different.

am I correct in "testing" ring land area with a 4.2 piston just as a temporary solution until I get the 4.0 pistons pressed to the 4.2 rods?

[sudo chop]

The 258 has a bore of 3.75 where the 242 is 3.895, so yea, about 4mm difference.

idk about the pin height/ring height on the 258 though, sorry.