I absolutely positively support the info from techinspector – the Vortec heads from Chevy trucks seem to be the best ever. I don’t know what kind of wrecking yard access you have, but these heads used to be fairly accessible for about $100-200 apiece. GM may still be able to get this part number for about $500 a pair. Private party will clean them up and sell them online for a lot more.
This Vortec head is an LT1 designed chamber. It has LT1 intake and exhaust ports with 1.94/1.50-inch valves. If you can in a good clean set (tight valves and springs), they perform well in their stock configuration. Everything that I have read shows they can easily produce 400HP with “off the shelf” Performer series manifold, cam and carb from Edelbrock. The casting number techinspector referenced is the only good one. 10239906 was also used for these truck motors and it doesn’t flow as well.
Key to remember is that this head definitely requires a Vortec specific intake manifold. Also, like a lot of Chevy heads, this one uses press in rocker arm studs (3/8”). Not necessarily bad, unless someone has reefed on them or you’re building a really monster spring/cam combination.
You also get to use the really cool center bolt valve covers.
Good luck on this project