Nice! I prefer personal experience and I don't have any, so I'm just regurgitating what I read years ago. The 6.4 cam swap "recipe" says the 6.4 springs don't work. Sounds like maybe they do though.
Ya it's been a while, but I threw a comp cam in an otherwise stock eagle with just stock, Chrysler dealer 6.4 springs and made around 480 if I recall. I locked the timing and ran it with a holley hp.