I figure that it's going to cost anywhere between $300- $500 to get the original head redone,if I could buy a good set of used high performance heads for just a little more money I would just go that way.I would think there are some good buys out there.
If you truly have a 74 302 and it's still got it's Grand Canyon dished pistons, you need to swap pistons too for aftermarket heads and cams to work properly. Otherwise you're going to have an engine with good heads but an 8 to 1 compression ratio. And that's not enough compression for most bigger cams.