OKAY, dudes, enuff's enuff!

May I point out that the scans of the Motors Manual pages show the 400's bore as 4.340 when we know it's 4.342. So why should we trust the 3.380 number for stroke?

The stock 400 bore by stroke is 4.342 x 3.375.

If I was running a high performance engine shop I'd be saying exactly what Dan is saying, balance the assembly.

BUT, if I was doing the work myself in my backyard I'd swap cranks and be done with it. I'd have only myself to blame if it didn't work out.

R.