I use 92 octane daily, sometimes when the wallet is thin a 50/50 mix of 87/92 octane. Engine work here is cheap, so that's no problem, getting hi po parts may be difficult so will have to shop in the USA for that stuff. And I have looked around for the 4.0 head, but never found one yet. I have been thinking about the offy intake. Nice to hear of someone who likes them, naver heard a testimonial before. Fuel injection is not a consideration cause I don't wanna put a computer in the beast. Prefer old school. As far as CFM, I need to be conservative at 10,000 ft altitude, real easy to run rich! And when I take the old girl up to the top of the volcano, yes, we have a volcano, and yes it was a gas in the jeep, i can smell the gas practically just pouring out the exhaust (12,000 ft). Thanks for the comments, and I would like to learn more about head work as I have always been a "bolt on" guy, and would like to advance my knowledge, push the limit a bit! Rob