[mpeastend]

I have a 3.8 (3.74 actually) with 12.5 CR. While I don't know how much is gained from going up one full compression point, I do know what the fuel needs are. The engine builder told me that for track applications I need to put in 110 leaded. I use the benchmark/standard...Sunoco purple. I was told that, in a pinch, for driving on the street where you are not using full throttle, and it's not too hot out, 100 octane would be acceptable, but to be very careful doing it as this is only in an emergency. For track use you cannot get away without using leaded fuel as unleaded only goes up to 104. This will limit your compression choices if you need a catalytic converter. Hope this helps.