the "Viper " truck engine is a whole different animal it is a cast block instead of alum , different cam , computer etc
CP you're thinking about the old 488s.....
As far as I know the SRT-10 Ram engine is the exact same engine as the viper. I know it is an aluminum block and has pretty much the same hp rating as the viper engine. It might be the same but I don't know if dodge changed the RAM's rating when they kicked the viper rating up a couple ponies. I would imagine that the only major differences would be the front accessories, oil pan, and exhaust......and even then I wouldnt think it was that different, if any. You might want to ask the guys at SRT10forum.com or I would imagine that Cody might know.
As for running one in an old mopar, anything is possible with enough time and money. What are you trying to accomplish....HP, awe factor, or just to be different? I have seen a couple e-bodies running viper engines and i am pretty sure they all had firewall modifications done to make it work. If it were me I would keep looking for a 6.1 or wait for the 6.4 crate because the new hemi is starting to get a lot of aftermarket support and would make for an easier install being that it is 2 cylinders shorter.
