318 head???

The 273 heads will raise compression on your 318, which is a good thing. However, the ports and valves are still the same size, so you won't make a heck of a lot more power, especially at higher RPM. But on a street engine, they will be just fine. And, it's a no-brainer if you have a set ready to go.

As for the cam, it would depend a lot on the rest of your setup, especially gears and converter. Personally, I would go a step milder. The Comp XE268, milder Voodoo, or even Hughes 1523 would be fine. Isky still makes a mild mechanical (E4) which I'm seriously considering for my 318 build.