If you are looking for a older bike to ride long distance, with a load, I would be looking towards the newer end of the spectrum. A 1990 model would have a 7-speed freewheel that would necessitate you either getting by on higher gearing and weaker wheels, or an expensive new set of wheels with cassette hub. the 2000 T2000 model shown above has a 9-speed cassette. I would look into the smallest front chainrings you can use on the front as well. I use a 26×36×46 set up with a 11-34 cassette. The 1995 model year is the first year with an 8-speed cassette. I've toured extensively with a 11-32 8-speed, they're quite satisfactory. If it were me, I'd stay 1995 or newer.
If you don't mind me asking; what are you planning? I have ridden all over the country and may have some insight for you.
As I said before. Happy hunting.