You advance the cam buy using either offset crank keys or purchasing a crank gear/cam gear combination directly from Cloyes with multiple choices. I'm sure you will be putting on new gears on with all this work. Using the cam you have selected and advanceing it 4 degrees will give you great bottom end and performance where you will use it the most. I can give you the Cloyes # after I get home. I run them in my 302 GMC which use the identical gears. The Tech guy on the phone had a raft of information on Chev/GMC 6's. I believe I still have the box. (one tooth is way too far)...Good Luck. JD
