Greeting GTO Fans, Looks like I’m going to have to pull the engine in my ‘65 to repair rear main seal leak. What’s the recommendations for a seal that will not leak? Also, because it has 10.75:1 compression, I have to add 2.5 gallons of 112 octane race gas per fill-up to prevent spark knock. That’s an extra $20 bucks per tank… on top of the 93 octane cost. I have not found an octane booster that is as effective or worth the money. While it is out of the car I’m considering having 9.0 or 9.5:1 compression pistons installed. Has anyone done this? If so, how much did it effect the engine’s performance? And… how much will it devalue the car? Thanks for your advice on this!