Bummed out
For all intents and purposes you cannot bore the 5.7L block from 3.920" to 4.055" (Some claim that about 1/1000 blocks can be bored that much, but the chances of your block allowing that amount of overbore are well, 1/1000.)
The most common sizes of aftermarket pistons are standard bore and .020 over.
Here's Wisco's list of 5.7 Pistons:
http://www.wiseco.com/PDFs/Wiseco-Chrysler-Hemi-Pistons.pdf
Here's both:
http://www.wiseco.com/Catalogs/Automotive/Chrysler.pdf
Note: I am not endorsing wiseco pistons, I am simply trying to show you what is available.
Regards,
Joe Dokes