What headers for 318 magnum in an A-body?

Summit headers; http://www.summitracing.com/parts/SUM-G9040/
Summit exhaust; http://www.summitracing.com/parts/SUM-680144/

The above, is *About* the cheapest and certainly the easiest way to do this. Unless you do not care for the full Summit exhaust, you can always purchase your own mufflers, 1 or 2 4ft. lengths of exhaust pipe and a "U" bend to exit the exhaust out the side to help keep the cabin clear of fumes. I suggest a set (sold in pairs) of these pipes that make clearing the tranny cross member cut out area a easy thing to clear.
(Chrome tips extra ;) )