I called ATK for more information and was sent to voicemail. After a day of waiting with no call back I went ahead and decided to pull the trigger with Mike at MRL. I do like the fact that he is one of the advertizing vendors on FABO. (I hadn't realized that until after speaking with him) So, 550 HP it is. After Mike gets it built and I get it installed, I'll post pics and probably track E.T.s.