D4 pony motor piston design

Hello,
I am working on a D4 2T that I got last fall. I am going to bore the pony motor block for oversize pistons. I ordered two 2F3664 pistons, but I got one from one place and the other from a different place. They are a little different from each other. They both have "CATERPILLAR" cast inside them and are both stamped 2F3664 on the top, but the one on the left in the below photo has a chamfer around the wrist pin hole and only 4 holes drilled in each oil ring groove while the one on the right has no chamfer and has 8 holes in each oil ring groove. Is one a newer and better design? Is one aftermarket? I would like to install a matched set but don't know which one I should find a match to.

[attachment=17670]5-5-2013 003.jpg[/attachment]

Thanks,
Brian

Weight the same?

I would say just order one more from the place you got those and then send whichever is the odd one of the 3 back, BUT there may be 3 different types😆

I just weighed them and one is just under 1/4 ounce heavier. Does anyone know what the effect of more or less oil holes is? I was wondering if lubrication or oil consumption was improved with one over the other.

Brian