swirl ports heads didn't come until 81-82 and have casting #'s of H95 and H99
what yours does have is exhaust air injection, the thermostat housing has a provision for a one way valve and the head has a hole in it next to the water jacket that leads to the exhaust ports. not good or bad, just a pain to work with if you want to port it.
what it did was inject air into the exhaust stream to allow a more complete burn of fuel in the exhaust manifold, kinda like having an air pump without actually having one.