I just put a set on my 78 (they were free). They are a decent quality and have thicker flanges than the regular "flowmaster" headers, and the collectors are decent. I have a set of Hooker Super Comps that are made of thinner steel in the pipes (but similar flanges and collectors) on my 80. The afterburners will probably last longer (thicker pipes), but I didn't like how close they came on the passengers side to the front shackle (Hooker Super Comps fit great) ***I installed the ORD shackle kit as the originals were tweaked. They are a considerably thicker and use bigger bolts/nuts, so that may have made the situation worse than with a stock shackle***. I had to grind the shackle bolt and the nut on the 78 to make the afterburners fit without hitting. I also installed poly mounts (motor and t-case in the 78 when I did the headers) and the headers still come very close to hitting the shackle, and probably would if I had the stock worn rubber mounts. Moral of this story.....They are a decent header, but not the best fitting (again maybe due to the bigger shackles, it may not have been that way stock).
Hope this helps