'97 Chevy truck used Vortec cast iron heads, GM P/N 12558059 with the smaller valves (1.84"/1.5").

Remember the Vortec heads require a different intake manifold.

Chevy High Performance did a 305 build up with these heads and an Xtreme Energy cam, Edelbrock Performer and a 750 carb and got somewhere around 325HP. As I recall, they also used Xtreme Energy valve springs and maybe some porting/polishing (very slight). You may still be able to find the article.