Smog Port Hole/Header Problem

I just put headers on my 78' 360. Problem seems to be that the header flages don't cover up the little smog port holes. So now I have a seriously nast exhaust leak. Any ideas on how to fix the problem/ fill the holes. I don't really want to take the motor out, and I don't really want to take the heads off either. Any ideas or experience would help. Thanks!