I would say dual sport. This is like taking a '68 Mustang. It might do fine, but it will be hard on the old girl. Your bike is going to be a classic very soon, if not already. You will take years off its life, years you'll want back some day.
Better to get a newer dual sport, something you can afford, and save your classic.
In my opinion, dual sports, especially the big ones are the standard bikes of today. Most of them are ridden on the road, many exclusively so. Like a standard, the just do lots of stuff well. Motorcycle marketing just won't accept a standard. It does not work with identity marketing.