Recessed valves

My suggestion would be to scrap the heads and either find another set of heads or if your budget will allow it, get some aftermarket aluminum heads. There is also a good chance that you will find the heads "might" have the beginnings of some cracks around the sunken valves. Having 8 hardened exhaust seats and new valves put in can get a bit pricey, whereas some of the aftermarket heads will be about the same price ready to bolt on. Just my .02