Help with 318 Build, please.

I am trying to put together a nice little daily driver that I can take to the track once and a while without breaking the bank. Don't laugh but here's what I have- 1975 Dodge Dart 4 door with 318. I've put a Weiand intake and 600 Holley as well as a set of Hedman headers in it. My next step is to install a mild cam and 340 stock heads-if I can find some at a decent price. First question is which cam to go with? Next question is what would be a decent price for the heads or is there a better/comparable one at a better price? I'll be doing the cam first then heads when $ money allows. Is it worth doing the cam upgrade before I get the heads or am I not going to see the benefits until heads are installed? Thanks for the help and looking forward to seeing what ideas you come up with for me!! Please remember this is a BUDGET BUILD! You all have been great here helping so far, keep it up, please and thank you!!!