definitely do a 402... The only way I'd overbore that block is with new sleeves... and then your talking big $$$$$ stock sized forged pistons and a nice 4" crank will be a nice setup.

 

A 416 is a 4.065 bore with 4" stroke, which is out of an L92/L76 block the 4.065 is the standard bore for it, but it costs a few hundred bucks more for the block over the LS2 plus he already has the LS2 block. For the 5 or 6 more hp that couple of cubes will get you since Im sure your combo will be fairly mild, its not worth the extra money IMO.