according to Raylar a set of heads alone added to the H.O. will already put you beyond the 500 EFI in H.P. and torque.. for A LOT LESS than 10 grand,,, and if it makes you feel any better, I'll buy you can of merc. blue spray paint..
P.S. if I had the cash for Zul's or Sterlings why even bother mentioning the H.O. ?? it certainly is not an option for a 42 footer,, unles you wanna run around WFO @ 60 mph..