318 and which cam?

I am doing heads for my 318 now - I'm swapping on 273 heads from the original engine. Those or the "302" casting 318 heads would probably be good for you. Instead of ~half a compression point, with milling you could bump it 1 or more points I think.

Honestly, I think the most you can do for these engines lies in the cam and heads, based on flow and compression. It might cost you another couple hundred bucks to change heads, but IMO it's a really good bang for the buck. You'll sink all that money into your current heads and probably not even hit 9.0:1 compression with stock pistons..you can do what I did, and re-use your valves, etc from the current heads, I just went with Comp 901 springs, everything else stock (XE268 cam).