Mine is double butted according to the sticker, with mounts for only one bottle cage, and no front lowrider mounts. I hear about triple butted Gran Turismos with lots of mounts.
I am really happy with my frame, but I wonder why they are both named the same, with such different tubing. Was it a change from one year to the next? Anyone know?

You will find lots of variation in this particular model. Some years had caliper brakes (ouch), other years had more desirable cantilever brakes. Do a search of this forum and you will find lots of info on this model, be sure to search by relevance, or it does not work.

I had a 1983 as I recall, sold it earlier this year. It did not have front rack braze-ons, and did have canti brakes. I think the tubing was double butted, not sure anymore. It was a really nice bike, just not my size (too small). It also had all Suntour Blueline components, which I like.