All you need is the top, door surrounds, windows, tailgate retainers, bow mount brackets, and the screws to attach bow mount brackets to the roll bar (those aren't too important because you can just pick them up at the local hardware store). below are some pics of the bow mount brackets and tailgate retainers.
I just bought a dual top soft top off of craigslist, so I know for sure what needs to come with it.
Sounds like he has everything except the tailgate retainers and the bow mount brackets. By the way, nothing is welded onto the jeep. The brackets just screw on under the padding on the roll bars, and the tailgate retainers just clip on to either side of the tailgate to hold in the tailgate bar in place, so you should be all set if he has those.