Has anyone ever seen this site?
www.somender-singh.com
I read his article in Popular Science a long time ago and it seemed legit, the info on his site and forum look good.
The groove lets you run high compression ratios on regular gas (10-11:1). This gives you more torque, so you can run lower rpms when driving for better mileage, it also decreases engine temperatures, so you can run lower octane.
I've been planning a 350 swap, so I figured I could do this to my 305. That way I won't feel as bad if it ****s out on me. And if it doesn't, all the better.