I run Panaracer protite 26 x 1.75 tires on my 1993 Bridgestone XO 2. They're good tires and work well for riding gravel.

I run Schwalbe marathon touring supreme 26 x 2.0 on my 1993 Bridgestone MB 1. They're fine all around tires as well.

I run Continental 26 x 1.75 folding contact travel tires on my 1992 Trek 950. They're very good tires as well.

I have a 1992 Specialized Stumpjumper on the build queue. I plan on doing a drop bar conversion. I haven't decided on the tires yet but I'll find something 2.0 or a bit wider for them.