Not that anyone would care much - but here is a pic of the V6 piston (left) and V8 piston (right).

Notice the relief(s) on the GT piston for the single exhaust valve. There are two reliefs so that the piston can be installed 180 degrees either way. It also has a partial skirt so it has less mass than the V6 piston (which has a full skirt).

 

I also read somewhere, and correct me if I'm wrong, that the 4.0 has forged connecting rods & pistons, where the 4.6 uses powdered metal rods and hypereutectic pistons. Go figure.

 

Not sure about the rods, but both pistons appear to be cast...

 

I'm not sure, maybe it's just the photo, but the bore of the V6 is 3.95" vs. 3.60" for the V8, yet in the photo the piston on the right looks wider to me.

 

You are right -

My mistake - the piston on the right is from the GT, but the piston on the left is a "2V" piston, not the 4.0 V6. Both of the pistons shown are the same bore. I was misinformed...

 

S'okay, I love being right

 

The 4.6 has Hypereutectic pistons with teflon coated skirts and powdered metal "Cracked Cap" connecting rods.

These rods are far stronger than the forging technology today while being lighter and more consistant in weight and quality. GM has been using this technology for quite a while in the LT1/LT4 engines as well as all of the LS series. The Cracked Cap technology give a precise and strong interface registration between the cap and the rod that will not fail or walk.

Absolutely nothing wrong with Hypereutectic pistons either. Lightweight - can be clearanced to under .001 skirt clearance - more HP, less blow-by. There's a number of really good reasons why literally every performance car today uses hypereutectics and it's not because they're cheaper..