In addition to the new harnesses miesk mentioned you can also just rewire it with a kit instead of using a prefab harness. I've used both the Wire-Works kit and the one from Painless wiring and they're both excellent kits that are cheaper than a replacement harness. I've done a few Broncos with the kits and I prefer being able to pull out all of the original wiring, PLUS the 30-odd years of accumulated additions that previous owners installed. I also like not having anything extra in there. The factory harness always seems to have about twice as much wiring as you really need because they use the same harness in just about every vehicle regardless of what options package that particular truck did or didn't have so there's always a bunch of unused circuits & connectors.
Having rewired one from scratch using nothing but a dozen big spools of wire I would strongly recommend one of the kits instead. They're very well laid out and labled so stopping for a day or two in the middle of the job will NOT induce a stroke.
But to actually answer the question you asked, sure you can swap in the harness from your 79. The cruise control shouldn't be any problem, there's a good chance the 79' harness will have the cruise wiring in it already. Might not because they did in fact use a couple different harness but there's a lot of overlap between them so you might could get lucky.
http://wire-works.com/showpage.php?page=ab...m&aboutid=1
http://www.painlessperformance.com/