I installed a lot of sunroofs "back in the day". It is an aftermarket sunroof, and swapping it is doable, but . . .
How old is the donor sunroof, and does it leak now? How good is the condition of the gasket? Sunroofs will need the gasket replaced at some point. Replacement gaskets were available when I did installations, but finding a replacement now could be like finding a needle in a haystack, or trying to adapt what you can find.
To remove the donor roof, if it's a typical older one, there should be a lower ring or surround piece on the underside. Remove all of the phillips screws and drop the ring. Pry the top frame piece upward from the roof panel. Most installations used tacky tape, a few called for RTV silicone. Either way, it'll be a wrestling match, and don't bend the frame or tear the gasket.
It's probably not braced. I used to add bracing if the roof felt weak, which was simply side panels wedged under the sunroof frame and then screwed to the car roof side framing (this was quick-fabbed from the metal removed).
Are you putting this in the '86? I think that yours has a double-panel roof, which is a real pain to cut for a sunroof. On double panel roofs, use shears on the outer panel, then stuff rags in the gap and jig saw the inner panel. You need to cover the interior, and don't let the raw metal shavings get loose between the panels. Shavings will cause rust rot to start from the inside later on, and that's why you stuff rags in the gap back from the jigsaw cut, so the shavings get trapped and can be cleaned out.
Finally, it is a valid concern about cutting a large hole in a truck that's survived 33 years. There are less and less of these trucks every day, and clean survivors will only become more valuable. That being said, it's your truck, so make it like you want it. I like sunroofs, although none of my current RBVs have one. If you really want a sunroof, consider investing in one of the higher-quality new ones, with spare parts support, and make damn sure that whoever installs it knows what they're doing.
Good luck!
Robbie
Welcome Visitor! Please take a few seconds and Register
for our forum. Even if you don't want to post, you can still 'Like' and react to posts. 
