I also have one registered as a 79, with the chrome bumpers.
1. If your choices are to re-core or buy another one, you could take it to a
rad shop and have it tested. I don't know the costs of new, but you could
check through The Roadster Factory (TRF) or SpitBits. Both have websites and
are identified in the Monster Vendor list that can be found at the S.O.L.
website (where you likely found out about subscribing to this list)
2. You could put some of the goop that resuscitates old gas, but if it were
me, I'd suck it out and use it in the lawnmower. As to having the tank
cleaned, I guess it depends on the shape its in. If you drain it out, and
don't find any particles of rust etc., and a visual inspection through the
filler neck looks all shiny inside, then you may be able to leave well
enough alone and save a few bucks. If you get lots of particles, I'd get it
cleaned (and maybe re-sealed, because you don't want the carb to get
indigestion from rust particles).
3. See above reference to the Monster List
4.Grind it down and re-paint it.
Hope this helps, many of the real experts are probably at Portland. (Colour
Manager, Training and Development