I assume he just wants to recondition his engine, rather than really modify it. I imagine not every block will take 3mm over-bore anyway.

I'm doing a budget modified engine and wouldn't bother trying to stretch it 3mm! I chose these 1.4mm oversize (76.9+0.50=77.4mm) because that's the cheap, readily available piston option here, gives about 1450cc and the basically flat top piston (after milling) ups the CR to work better with a cam grind.