I've owned '83 and '85 Celica GT-Ss, both of which had AC installed sunroofs which are very similar. The lower end of the rear drain tubes connected to rubber drain grommets (similar to that of a firewall A/C condenser drain) in the lower quarter panel extensions which allowed any water to drain outside the body structure.

What does the rear, lower bracket bolt thread into? On my Celicas I recall the tension spring (which is supposed to lift the rear edge of the sunroof panel into position as it gets close to fully closed) would lose some of its spring over the year and had to be re-arched.

Does www.sunroofdoctor.com carry anything you can use?