In need of some 273 head education

I am looking to rebuild the 273 in my dart and i would like to do it fairly cheap but at the same time increase the power over stock specs. I assume that there were different heads put on these through the years and was wondering what they would be and the part numbers of them. I do not have the casting numbers of my heads right now or i would post them, but can get them by monday if that would help. I also wondered what it would cost to get some work done on the heads that i currently have to increase flow and wether or not it is worth the money compared to buying a used set of higher flowing heads or by putting money into the bottom end to increase power. Thanks!