According to the 1987 Trek Catalog, the main tubing is Reynolds 531; Trek just chose to hide the 531 lower on the seat tube. I have the 330 Elance, also Reynolds 531, Trek lugs, and "Tempered" stays. With an Ultegra 9-sp group and Ksyrium Equipes, it's a shade under 22 lbs. Great stability, but agile enough for a pace line. You have a fine bike, as is, and a great platform for whatever you want to hang on it.
http://www.vintage-trek.com/TrekBrochure1987.htm