Broken Bolt

well thank you all for the replies it seems my Darts gonna need a set of valves :/ my dad and i took degreaser to it today really cleand up good :) and we got the bolt out my hand with a really big pipe wrench. the gears no longer have plastic teeth there gone its a pretty big mess in there. I guess i have to take these heads to a machinist i cant just slap new valves in which sucks due to the money issue im going to have with this ( ill tell you on a teenager budget a old car really kills on the money) im thinking of either going with junkyard heads or something im not sure what a proper rebuilding of the heads is going to be like as far as money id like to have a private party do it if anybody knows a good rebuilding please PM there info i thank you all for your help ill post a picture of the gears on Monday