Going with BIGGER pistons? You'll probably want to go with a larger diameter head gasket. Weak and cheap head gaskets can lead to loss of power and meltdown if you're not careful. These are MLS multi-layer metal gaskets suited for big cylinder bores and pistons and designed to hold up to high power output that these motors can be capable of. The stock gaskets have a cylinder opening of 92mm. You should use these oversized gaskets if you are using a piston that is larger than 92mm (larger than a .040" bore).
NOTE: These same gaskets also work on the 6G74 blocks for those doing the 3.5-liter conversion. The stock bore of that block is 93mm, so if you are using a 93mm piston, these 93mm gaskets are what you want. If you are boring the block for larger pistons then you will want the larger 95mm gaskets.
All gaskets are the stock .051" thickness.
We do offer the Cometic MLS head gaskets in a wide range of bores and custom thicknesses to suite your specific engine needs.