What headers for 318 magnum in an A-body?

I have heard guys who say that the one tube that hangs low on this install that they measured the distance between the header and the road and it was only 4 inches off the pavement. The only real solution is to build a "skid plate" like the ones on 4wd trucks. The problem has become so bad that several header companies are offering the drivers side only header.
I would like to suggest using manifolds. I was in exactly the same situation as you I needed to choose an exhaust set up. I made a list of pro and cons.
Cons

Access to plugs 5 and 7
Lots of heat coming from the floor, will need fatmat or something like it
periodic gasket replacement
periodic paint/coating
need really good plug wires because of the heat
overall fit, may have to ding or resection sections of pipe
crunching them because they hang so low

pros

extra horsepower
no substitute for the delicious sound of headers
easy to find the rest of the system mufflers, pipes, etc.
good horsepower per dollar spent

I spent weeks trying to make a decision and went with this set up:
a 340 (68-71) exhaust manifold for the drivers side
a 360 Magnum exhaust manifold on the passenger side

I was concerned that the manifolds were mismatched in terms of flow until I found a website where a guy had run dyno test on 340 and 360 Magnum manifolds. There is a difference in the Magnum manifolds. In 92-93 only the RT Dakota had a 360 with manifolds that were 2 1/2 outlet. The horsepower rating dropped 10 horsepower from 94 on. The 94 on manifolds have a 1 7/8 outlet with the outside appearance almost identical to the larger outlet manifold. The dyno test showed that the 340 manifold was VERY close in flow to the 360 manifold.
I realize that I am losing about 20 horsepower by running the manifolds instead of the headers, but will make it up somewhere else. By the time you buy the headers, gaskets, collectors, mufflers, etc. and get everything installed you would pay less for a 3.55 or 3.91 ring and pinion. The biggest horsepower gain and the biggest bang for the buck was going from a 2 barrel to a 4 barrel. The second best bang for the buck is changing from say a 2.76 to a 3.91. Why don't you put the header money towards lower gears. Seat of the pants feel and actual performance would be greater with lower gears instead of headers. You will get more bang for your buck going with gears instead of headers. I have seen guys get more than a second quicker in the 1/4 by doing a gear change. 20 horsepower is 2/10 of a second in the 1/4 which you might feel. Going a full second faster is DEFINITELY something you would feel.
If you're mind is definitely made up for headers, I agree with Rumblefish. Summit headers are very reasonably priced. are not too bad on fitment issues. You could spend 5-600 for TTI headers which don't involve the link but I rememberd that you are like most of us, want to go fast or boil the hides, but need to do it on a budget.