Allright guys, I've heard about this for a while but can't seem to find much information on it. What it is is that milling a slot into the head will add performance and increase fuel economy. I believe that the groove just goes from the spark plug to where the center of the piston is. Any advice would be welcome, I'm considering doing this to my truck and also have them milled down to get to some modern level of compression.

I have not heard of this. I will have to check in to it and get back to you. What is the idea behind the slot? How is it supposed to increase performance?

It's a groove that goes from the combustion cup where the spark plug is to to the outside wall of the Cylinder. The idea is to help funnel the flame towards being over the piston, this seems like it would help as there is 2 or 3 inches from where the spark plug is to where the center of piston is. Some people say that they get as much as 25% better fuel mileage (somewhat believable) and as much as 50% power increase (hard to believe it's that much).