The 392 cover won't fit the 5.7L, it's a totally different intake design and it won't allow for the placement of the throttle body on the trucks. Best be is to paint the OEM cover, several people have done this and it looks very nice. Me, I just swapped to a 6.1L intake manifold that's p/c brilliant black.
3GCustomz has a nice set of half covers that are available for the 5.7L RAM so it'll at least cover up the coil packs. You can also shave down the plastic cross hatching on the intake manifold and then paint it as well if you want to clean up the engine bay a bit. Here's the link to the half covers: