If you want some good low budget heads, there's a guy selling old Chevy 2.02 heads at almost every swap meet. They're usually the old "camel hump" heads and he sells them for $300 a pair. They have all new SS valves, hardened seats, and are fresh to go. With those heads and the other changes you can easily go over 350hp.
I'm sure he'll be at the Portland Expo swap meet if you're planning to hit that one. I'll have a space at the race track area this year.