5.9 Magnum out of manual truck going to work?

Hey guys I just put a deposit down on a Magnum motor out off a Ram 3500 manual transmission truck. This is going into a Duster. I read the 5.9s are externally balanced and balance themselves through the flywheel. I won't be getting a flywheel so can i just use anyone from a junkyard or does it need to be balanced to match my specific motor. i plan on putting a 904 auto behind.

Do you guys for see any problems or is there anything I should know or look out for ahead of time before I jump all the way into this?...swapping out of a manual truck into automatic. And will a manual crank bolt to automatic transmission or is there any difference?

Thanks