With the older heads and/or 10.0 or greater, plan on mixing in some racing gas. I do NOT recommend the lead additives, or you will find out in a hurry what it does to your plugs. Moderate use of Octane boosters is OK, but don't think you can go from 89 to 100 octane by dumping it in. My 77 pinged the day I took it home 29 years ago, and a simple Distributer recurve and carb tuning really helped! When I bolted on the older Ram Air Heads, the only real safe solution is the correct octane level, or you can kiss your rings and pistons good-bye!