The stock 6.4 cam is great, I have swapped them into eagle 5.7s and they work great with no need to limit the VVT or even delete the MDS, you get the best of all worlds. They recently increased the price by double butt it is still a steal compared to aftermarket stuff. They work with stock springs and will still give a good increase in performance even before you tune it. With a tune they turn a 5.7 into an animal. Also don't listen to the MDS naysayers, I see lifters go bad frequently in 3/4 and 1 ton trucks that have no MDS system and I see bad ones in the non MDS lobes in the MDS engines, actually seems the MDS lifter lasts longer. I have torn apart far more of these engines than most of the youtubers and internet forum chatters who heard of a guy who knew a guy who had a bad MDS lifter.