I can't think of a good reason to lower the compression unless the fuel quality in your area is extremely poor. I think you would be better off to retard your timing and readjust your carbs if you want to run lower octane.

If you're asking about one of the IPD performance cams, I'm not sure you would want to go that route if you're looking for better fuel economy.

Why not focus on improving the operating efficiency of your engine, and modify your driving style a little, if you haven't done so already.

Try a set of K&N air filters for starters. Some people claim better fuel economy with electronic ignition; I can't verify that though. If you do a lot of highway driving you could add overdrive, or change your rear axle ratio.

Go with a thermostatically controlled electric fan instead of a fixed fan, that will save a little power. Lose weight (ha ha!).

I'm rather interested in trying to get the best fuel economy I can too, but I'm not willing to give up any horsepower. The most effective thing I've done is to change my driving style, which is really difficult to stick with sometimes because the twin Mikunis sound so nice when I stomp on the gas ;)

Bill