So, playing devil’s advocate here. What if the last shop who had hands on it did everything right, and the seat failed from me driving it so hot? The driver side valve seals were all pretty burnt up, and I know for a fact the headers on that side had a leak after I installed them.
While it is possible, it is not at all probable that overheating was the cause. It's far, far more probable that this failed due to poor workmanship.
BTW, you actually got quite lucky with this failure. The usual outcome is that the seat drops, jams the valve open, the piston hits the valve repeatedly and eventually breaks the valve head off, which tumbles around, eventually jamming sideways between piston and cylinder head. At that point, the head busts, the piston busts, the rod bends, the cylinder wall cracks, or some combination of those things.
So IMHO, it's risking terminal engine failure to use these again. And I'm pretty dubious that these can be re-worked with new seats that will hold in unless you go to larger seats and valves (which certainly is possible). But with all that, it is a good time to re-think the head selection options, at the very least. Your budget and how you want to use this engine/car ought to be stated.