Next to the 906's the 452's are the preferred open chambered heads for the 383/400/440's. They should already have hardened exhaust valve seats. Strip them, inspect them, rebuild them and pocket port them and they'll support 475-500HP.
Here's a good article on BB heads, start to finish.
http://www.moparmusclemagazine.com/techarticles/5115_cylinder_heads/index.html
Terry