I took apart my relatively virgin 70 340 six pack engine, and although I can't remember the exact numbers, because that was over 40yrs ago, I was shocked how different each rod was. I think it was like 80 to 100 grams(if not higher) off from highest to lowest. I never noticed any bad vibration problems.
Maybe some other parameter? I checked an original rod set from a 340 and got 5 grams heaviest to lightest. 4 grams variation on the small ends and 3 grams on the big ends.
