Rear wheel hubs from the 86 can be used on the 85 to make it wider, front fork tubes interchange (not the triples), the front brake caliper and mount interchange, the rear brake caliper will work if you use the 85 bracket, complete front wheel and hub will fit the 85, the front master cylinder will work on the 85 (use the 85 brake hose). I think the headlight and shroud will fit the 85 and it looks nicer IMO. You could use the handlebars, clutch lever and thumb throttle on the 85 and maybe the carburetor with some jetting changes. Other than this stuff, nothing else I can think of.
Don't worry...just run watcha brung...