I think you’re right. The seat stay caps look more like the T-500 to me. Yes, the stays have what’s left of cantilever brazeons as well as the fork. The T-500 lists Suntour rear dropouts and a Bridgestone hi-ten fork, which I would presume could/would have Bridgestone dropouts. So, it is probably the original fork. There is a lot of paint on this frame. It took a while just to sand down to the Basso decals.