Direct swap of the blocks. Every nut and bolt swaps right over. My 6.4 SRT8 in my ram 1500 is a BGE block with all the SRT8 parts in it. I think the factory has switched over to running the BGE blocks in the latest SRT8s.

The 6.4 cam is pretty good already. I would go old school and shave the heads .030 (gives you about .5 compression and a little more pre-load on the lifters to keep ticking down), maybe swap in some long tube headers and 85MM throttle body. The factory long block without pulling the valve covers can get around 580HP with the really tall intake (eddelbrock and holley have shorter EFI manifolds that might get kinda close, I actually prefer the factory plastic one for the street because it don't heat the air as much as the aluminum ones), long tube race type headers and appropriate tuning.