[undy]

There's two basic style gaskets out there, one for the pre-65 FEs and one for the post-65 FEs. It depends on the age of the expansion tank and manifold age/design. The post 65 later ones are for the late model diameter (small) thermostats and the early ones use the early BB Mopar/early FE large diameter thermostats. My expasion tank originally took the early style and I had the tank flange changes to the later (small diameter) style. Confusing, isn't it ...??

Dave