I wouldn't go 42x anything unless it was with an ERL block. I'd stay 416 or any combo with a 4.0 stroke and not more than that. Thats just my .2 though.
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.