Jim Brock on this site sells custom made snail/log gaskets and are better than the standard green you'll find. I've removed several from the easiest to the worst... soak the studs and gasket with penetrating oil, then start tapping in the gasket with a steel spreader /gasket scraper. Once you have it in soak the studs from the inside. A bit of muscle with a pry bar back and forth either side and done. Be careful not to harm inside log flange.