To be honest, There is a lot of panic over runnign aluminum heads. Will they conduct more heat from the chambers? Yes. Will the better design ports and chambers make more power? Yes. Will they weigh a lot less? Yes. The net gains are much more than the net loss. I say, run 'em. You wont be disappointed, and you'll be able to run the cheapest octane easily...lol. Also, like was said, the finish of the surfaces is extremely important with any MLS gaskets. So unless your block was initially decked with the use of MLS in mind, you will need to mill the heads and block to getthe extra smooth finish they have to have.
