The bore is already set and that is on the block. Your bore is a 4.065.
You mean your Combustion Chamber size to run an xx compression ratio?
If your going for big boost I'd do an Ls3 conversion.
Just my .2
2001 ws6, 40k miles, Ls3 416 stroker, short block built by PER the rest by me. LPE Ls3 heads milled to 12-1 comp, FAST 102, NW 102, kooks 2", dual DMH cutouts, Magnaflow C/B, BTR cam + springs. Full UMI suspension.