A lot of those cork gaskets are glued together from several pieces. You could cut it and section it back together. I’d cut it on a bias for more glue area and use contact cement or CA glue on the joints. I also contact cement them to the rocker cover on my BBC stuff and use nothing on the head side. This will hold the glue joints and also let you remove the cover and use the gaskets multiple times. I’m still using a set of metal core cork gaskets that are 23 years old now and they’re off several times a year for maintenance with no leaks.