Catalytic Converter on a 65 Slant 6?

Sometimes,the exhaust fumes can creep into your car,like from small holes in the firewall,or they can creep into your trunk and make there way into the cabin.Every old car Ive had,even when I rode in my parents old cars when I was a kid had that old car gas smell.I guess im just use to it,lol.:dontknow: