Cam selection depends heavily on what your application will be. That sounds like a weasel answer but it's true. The choices are quite different between street/highway use, drag use, and race use.
Street/highway means you get it out of your garage and drive it around public streets, making stops and (mostly) observing sane speed limits. Drag use means you trailer the car to the track and use it for 1/8 and 1/4 mile runs. Race use means you run it in circle track races on closed courses as quickly as you can make laps. Those are my definitions, others may offer different interpretations.
For street/highway use, you want your engine's peak torque to set right at your normal highway cruising speed. Peak torque happens to also be the point where your engine has its highest volumetric efficiency, which means you will get your best fuel economy at that point in real-life driving. It will also have it's best throttle response at that point, and you'll find that the car moves away from stops much quicker than it would if the peak torque was higher iin the speed range. You'll still retain some decent top end, but it won't be a Bonneville Salt Flats racer.
For drag use, you want your engine to make its maximum possible horsepower and the transmission/rear gear/tire size to all work so you don't run out of RPMs at the end of the run. There is considerable art to those selections, and I am NOT a drag racer, so I'll leave the description of all of that to others.
For race use, you need your HP to fall in the speed range you'll be making to be competitive. Obviously, that varies with tracks and courses, so those guys do a lot of cam changes and rear gear changes. Again, I'm not a racer so I'll leave description of those details to the guys who are.
You sound like you want a street/highway car, so my advice would be to decide what rear gear/tire size you're going to use and compute how many RPM that requires to drive it at your normal ihighway cruise speed. Practically speaking, that could be anywhere from 55 - 75 MPH. Then I'd find a cam that develops peak torque as near to that RPM as possible, and use it. If there is more than 1 cam make/model that falls out of that selection process then I'd look at the width of the power band and pick the one that's the widest. But that's just my twisted sense of the process -- YMMV.
EDIT -- with due respect to RainMan, if you put the cam in that article in your 400 it won't run on the street very well. It has its torque peak at 4,000 RPM, which works out to be 91 MPH using a P255/60/R15 tire for your peak torque point with a 3.42:1 rear gear ratio. Conversely, to drop that to 70 MPH you'd need a 4.46:1 rear gear. Additionally, that cam provides for lift in the 0.550"+ range and your heads won't flow enough to need more than anything over 0.475" (or thereabouts). That's just too much cam for a streetable Pontiac 400, IMHO. Just my $0.02.