Some help with a 400

RustyRatRod said
400 block, stock 440 crank and plenty of people make off the shelf pistons.

I had heard that when you use a 440 crank you grind the hard metal off for the offset and it weakens the crank. Never looked much into it however, would I use the 400 rods or the 440 rods? Sounds expensive for machine work.