Performance was in the catalog business at least as far back as 1984 and had their own frames even back then. Indexed, 6 speed, 105 should place it 1987-1988. Tange 1 or 2 would use a 26.8mm post. If you're lucky the fork's steerer may have a Tange embossment and a date code. I'm pretty sure that I don't have any Performance catalogs from that era, but I'll check.