I painted my head with POR-20 (Paint Over Rust)..... it's like the POR-15 for body panels, etc.... but this stuff is rated at 1400 degrees!!!!!
It comes in 8oz cans, quarts and maybe larger sizes.....
and three colors.... black (1200 degrees), cast iron/factory grey (1400 degrees) and brilliant aluminum (1400 degrees).
my 8oz can was $30.
I had to go with brilliant aluminum because they were out of factory grey ..... but it doesn't look too bad on the head. I'll do the exhaust manifold, too.