Which type headliner does your 80 have, one piece or cloth with bows?
One piece is easier to remove but still need two people so it doesn't fold/bend near the sunroof hole.
One method for a
quick/temp fix, if you have the one piece headliner, first pull down the u-shaped thingy that goes over the pinch weld and the edge of the headliner, then gently pull the headliner down enough to slide in a fireproof welding type cloth under the hole (so you don't set the headliner on fire).
Then using a grinding wheel, clean up the rusty area some more (the rust extends well beyond what is seen in the photo above). With a dremel you could cut out the very thin edges of the rust hole, then re-apply a rust converter like OSPHO or RustMort. Then take a section of metal mesh screen you can find at any parts store even Wally Marts, stuff that in the hole and slather some steel reinforced Bondo over it (JB Weld worked for me on a much smaller area on the rear hatch), then sand, seal, prime, paint. Won't look professional (not many people will ever see it up there) but it should last at least a few years.
Others may have their own method, FWIW.
A very good rattle can primer (non catalzed) is, IME,
Transtar 2 in 1 primer, it's much better (binds/seals) than anything off the shelf from the parts store or Wally Marts. There are also a few brands of 2k Epoxy primer and 2k Epoxy topcoat (generic white).
For a matching color 2k topcoat there are companies that will mix up catalyzed paint (Toyota 045 for your white 80) in a spray can which is also much better than anything off the shelf.
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Already mentioned above, to fix it right; remove the headliner, cut out the bad section, flange the edges, and weld in good sheet metal, grind, sand, seal, prime, paint.
The link below shows how to use a flange tool to create a ledge for the new metal to sit on, then spot weld through the punched out holes.
Start watching around 4:00: