i would do the supercharged 6.4
but IMHO the charisma of the "10" is derived from the Viper V-10. kind of makes it.
and i am sure with the advances you could make a ram with the new 6.4 keep up just fine and fast enough, but could you imagine them with the Gen 4's.
WOW. bada$$.
You can't really mod the Gen4's because of all the computers and shit... can't tune it. That's why you haven't seen many boosted Gen4's
The 6.1 or 6.4 can be modded to hell and back cheap compared to the 10.