quick 318?
With the 2.02 valves, I hear people mention valve shrouding. I've heard some say it wouldn't be an issue. I don't know because I've never tried it... Only read about it.
For camshaft selection, I picked out a Howards for my Street/Strip purposes. I may step it up in size depending on how things go.
http://www.summitracing.com/parts/hrs-711915-12/overview/make/dodge
Aftermarket casting? Heads from Hughes Engines would fall into this category?
I have never had a 318 apart with a 2.02 head on it, but they are only a 3.91" bore as compared to a 360's 4.00" bore, so I can't imagine valve shrouding to be a problem (unless you are talking about the valves shrouding the chamber, not the bore, in which case its even more of a reason to get rid of those heads).
Hughes has aftermarket castings...I believe the iron rams? there are the RHS/Indy x heads also...I would keep my eyes peeled for a used set of W2's- they usually come with rocker gear, and finding headers and intakes for them is not difficult at all, and best part is they work well and are affordable. Just do your research as there were a lot of variations...Even used or NIB second hand eddy heads would be nice...Again, this stuff is not a necessity, but after doing this stuff to my car, I would keep what you already had until you were ready to step up to this stuff instead of trying to jimmy with the stock stuff.
Not sure what kind of rpm you are turning or what your compression is, but that cam is SMALL, I think personally even for a 318. And a hydraulic roller + rpm with a mopar's horrible stock lifter angle do not work well together unless you run a real real stout spring package at which point a solid roller would be the way to go (and the only way to go imo).
As was said, if you want a 318 to really run, its going to need some gear, a looser converter, and to rev to make the power. Just look at every 302 in a mustang- unless it runs a power adder like nitrous or a supercharger (and nothing wrong with those either), the N/A ones are right along the lines of where a powerful N/A 318 needs to be.
Again, just my 2 cents...I am no expert, so take it as you will