I have taken my block (350) to a machine shop to have a .030" over bore done. I thought it would be as simple as getting that done. But they said they would really like to have the pistons and size the bores to them as they reckon pistons can fluctuate by .005". My question is does it really make that much difference to a street motor? I was not banking on getting the pistons yet. Should I take their advice?