The rear shocks can be rebuilt, but I think you have to cross-reference the right parts because I believe the actual Tecate parts have been discontinued. If you want somebody to do it for you, SBLT500R here on the boards does it. I think you COULD use the 86 plastics on the 85, but I'm not quite sure how they would mount up. Personally I don't like the 86 plastics on the 85, but that's a matter of opinion. The best way to restore the tank is to wet-sand it. I've never done it, but numerous people on here have.
85 Tri-Zinger 60
85 ATC250SX
86 ATC250SX
87 ATC250SX
02 XR650L conversion
84 ATC 480R