I wouldn't think there would be much difference installing one in a third gen than there would be in a first or second. I put a TCI in my 65 and when I started I'd never done anything like that. I also went with a nine inch ford rear and when I bought my four link and got my measurements I sent my four link brackets to the guy who built my rear end housing and he installed the four link brackets. When my housing arrived it was ready to mock up before paint/powder coat. I followed the instructions and it really wasn't too much to it. Mine was on a rotisserrie which made it a lot easier. A lift would also make things easier. We did a Mustang with the torque arm on a lift and it wasn't bad either. I have around four thousand miles on mine and nothings fell off it yet.
There are several companies that offer a bolt in four link type system. If you are talking about a real four link with formed rear frame rails with integrated cage and all it's a completely different ball game. That would be a lot more complicated.