If its just going to be a street engine in the neighborhood of ~300 hp, a set of stock magnum heads might be the way to go.
They actually flow a little better than most stock 360 heads (which is already far better than 318 heads), but have closed chambers with a chamber volume around 60cc's, so your compression stays up. They come standard with 1.92/1.60 valves, which beats the hell out of 318 heads but stays away from any shrouding effects that some folks claim you can get with the larger 2.02 valves in a 318. And they're cheap and readily available. You will need some oil through lifters and push rods, and a new magnum intake manifold. They also have different rockers (1.6 ratio, and not shaft mounted), so be aware of that as well.
Now, this is just comparing stock heads. If I were looking at having larger valves installed or any porting done or anything like that I'd just get a set of the RHS heads and be done with it. But if you're on a budget and are looking at 318 heads, 302's, or magnum heads I think the magnums are the way to go. And if 300 hp is a good number for you, the RHS heads are going to be overkill. Also, if this is a street engine, you'll probably want to keep your compression ratio at or below 10:1 to be safe for pump gas.
