What is your intention with the truck. Is it a long term purchase or a 5 year type of thing?
If it's long term and you intend to drive it well past the warranty; then put in 0w-30 or 5w-30 because IMHO it's more important to worry about the life of your engine when you have your truck outside the warranty. There is less probability of needing your engine warranty, and nobody has demonstrated (to my knowledge) that warranty work was denied on a 5.7 hemi simply because of running 5w-30.
These hemis have a known issue with lifter failure. Still only a few percent get the problem, but it's something to keep in mind. Probably your best bet against getting the issue is to run a high quality oil that both protects and cleans extremely well, as the needle bearings might be failing due to crud/varnish getting in the bearings. I choose to run HPL's oils, the premium passenger is an excellent choice (as is the cheaper PCMO) which "meets or exceeds chrylser ms6395" and you can get it in a 20 weight if you wish. (The premium just has better cold start properties which is why I chose it over the plain PCMO, you may not need to worry about cold temps where you live.)
It's expensive oil, but you can (in theory) run it longer in your engine and if you're willing to pay $40 every time for a UOA then it's not a far leap to run a more expensive oil either and get the absolute best of the best for your engine.