Sounds like a nice bike. Vintage Treks do have a following, but prices are not stratospheric yet. I'm sure someone would spend several hundred dollars for that frame, given that it's full 531.

You might try contacting Skip at vintage-trek.com. He's very friendly and responsive. I have a '79 Trek 530 which doesn't match any of the brochures, and investigating that, I learned that early on Trek was a very relaxed framebuilding outfit that operated much like custom frame builders today. It wasn't at all like the modern Trek of today, where standardization rules. Apparently, my frame was either a custom build or something that was built with spare frame parts. It may be they had frame parts leftover for 50 more 730s from 1982, and simply finished them up in 1983.

I think CampyGuy's theory may be right, given the eclectic mix of components on your bike.