Does it look like this?



This is my '88 660. It's a 19in, according to vintage-trek.com. Sounds like the same measurements you have. It's a little small for me, which I've overcome with the 120mm stem and a fist-and-a-half of seat post, but it still is a very comfortable ride.

You can see that I've converted it to fixed gear but I might throw the derailleurs back on. And put some wider touring or cyclocross tires to be able to ride some packed gravel and dirt. These are really marvelous adaptable bikes.