The problem is, like others have said, there's no magic 'right' cam. It very much depends on what you want to do.
"best" for a car that will never see a dragstrip is different from "best" for a car that will get slicks and back-halved with a powerglide.
You really need to nail down what you intend to do with the car, and go from there. Do you plan to run headers? Do you have speedbumps where the car will be driven? Do you want to lower the car? Do you plan to drive on the freeway? What kind of MPG do you consider reasonable for this car? Does your budget allow for machining heads for new/better springs? What kind of heads do you plan to run? Intake? Carb? EFI? All of these are just the beginning...
If you have speedbumps, you'll want to plan for headers that don't hang so low. If you don't, you have more options. If you're going to be on the freeway much, you'll probably not want to turn 4,000 rpm at 70mph, and so you'll need to figure out what your 'max' cruising RPM is, and figure out gearing from there. Or decide if you want to install an overdrive trans. You'll also need to give an idea of what kind of wheel/tire you plan to run (to help determine gearing). Do you have a budget for new gears? What rear end is in the car now? Do you plan to lighten the car, or leave it stock? Also, what kind of car is this build going into?
If you don't want to run headers, then you'll likely be quite disappointed in anything beyond a modest cam upgrade since better scavenging during overlap relies on longer primary lengths the headers provide.
You've mentioned wanting to run a magnum 5.2 or 5.9 in the future. There's not a ton of off-the-shelf roller cams available for them, but there's some decent ones - if you have decided to rebuild the 318, then you'll need to see what you can do for compression first before picking a cam. A stock compression 318 can give very disappointing results with the wrong cam in it.
In order to get the best guideance, you'll need to get very specific about what you want to do with the car and the type of driving conditions you're likely to encounter. There's plenty of very helpful members on this board who can help you pick a winner - but you need to help them with more and better info.
Calling the various cam companies will help give you ideas, but you'll need to be specific with them too. They're going to recommend something different to someone who will be racing every weekend versus someone who tows a tent trailer each weekend..