Those look like a Trick Flow LS head? Ouch!!! Aluminum head repair gets expensive quick. Welding the chamber puts alot of heat in the valve seat area which distorts everything and usually requires re-heat treating the casting and remachining the seat bores. You sometimes have to replace all of the seats and guides to do this (depending on what is truly there). Its hard to tell from the pics but that is potentially what you are up against. I don't do much head repair like this currently because some of the equipment required to do so (mainly the heat treating part). I do have a couple of people that TIG weld for me but I don't think I would be interested in this one. Have you looked into the cost of getting a bare casting? Sometimes, especially with the cost of the LS stuff it is more cost effective.
It is definitely fixable. You may try these guys in Nevada, Iowa -
http://www.midwestcylinderhead.com/