castech heads repair

Ok need some help fellas ive got a 04 Tahoe awd 5.3 just found out ive got the castech heads and they have a crack in them. dealership cost to repair and buy two brand new heads and button back up around $3000 or so. Should I just get some aftermarket heads or maybe 243's is what ive seen on here are a good option and put a cam in it? or just go back stock? I would love more power but I don't want to lose a lot of mpg's at the same time and I know if you increase hp you gonna lose mpg correct? Also if I put heads and a cam on it do I need to go ahead put headers on it too? Any suggestions would be greatly appreciated!