<~~~ Obviously im still new here, but i've got the same problem with my 87 Teg, but on a 400% scale. A buddy of mine that owns an autobody shop told me the best thing to do was to buy back quarter panels and weld them on. I know its a Unibody construction but they sell kits to hack off the lower aft panels and weld on new ones. As long as your rust hasn't gone above the back quarter windows your golden. NOTE: Check your wheel wells to.
My Teg would only cost about $120 Canadian for both panels. That's about $100 american.