The answer on which rods to use depends on several factors. First question is which rod journal does your crank have? If you have a BB Chevy rod journal then there are more options than if the crank has Mopar journals.

I'd probably use a 6.70 long BBC rod but it depends on the piston choice as well as other things. The 440Source 470 kit uses a 6.535 rod which is an okay choice also.