Wayne...I don't think you need to worry about the older 166 motors. When we had the Ozark Mountain Midget Series going we had such a wide range of engines racing with us that I couldn't even begin to list them all...including a few older Geartes and Fontanas, and plenty of times a 1000cc car was sitting in victory lane at the end of the night. I am pretty sure your harder RR rule and weight rule will be more than sufficient to balance the field out... and the fact that you already stated you may implement a tire pressure rule if there is a clear advantage should give everybody the confidence to come on down.

Keep doing what you're doing...you are on a great path.