Some help with a 400

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.

You "heard" wrong. Build what you want to. Andy is right, though. A 400 with 3K dollars worth of heads will haul ***.