Pacesetter dosen't make it anymore. I already asked them. I don't know of anybody who makes an after-market exhaust header for the '79-'84 B2000. Believe me, I have been looking for one for quite some time.
get some 3/8" plate steel, cut it out for the flange, get you some pre bent pipes, and make some. i do know offenhauser makes an intake manifold for those trucks, and you can get one from summit on the cheap.
They do have the intakes just call them, on thier webpage it doesnt give any description so I called them to check and they said the years for the offy intake is 79-84.