Since the valve timing measures great, I wouldn't touch it (ain't broke, don't fix it). I am guessing the mechanic could see the tensioner by viewing down the chain cavity. I don't know how to do that. I don't think there is anything external on the engine to view the adjustment. I thought it is just a spring, with no screw adjustment. A lot of people here say "just do it", "good insurance", ... but you must do the work, search & pay for the parts, and risk making things worse.

If worried about an offset key, you could remove the bolt & washer on the camshaft end to see if there is one. Regardless, if "start of fuel delivery" is off, you can adjust that separately. It is trickier to loosen one of the 3 mounting bolts on the IP on your 85 with the silly "rack position sensor" on the side (used only for EGR controls).