I like Comp cams additive, you can get at most auto parts stores. I drive less then 1000 miles a year and my oil is at least three years old. Probably time to change it I guess.
As long as you run the truck long enough to dry out the oil, two to three years shouldn't hurt it. Just be sure to get the truck hot each time you run it. I won't start mine unless I am going somewhere, just cleaning the garage or something like that, I push it out and back in. This also helps keep the exhaust pipe from rusting out. My brother has a '69 barracuda he doesn't drive much, oil in it is going on 10 years + and still looks clear.
Joe
