I am in the process of buying an 85 supra, however a couple of issues do exist.

1. Car will not start. New battery was installed. When turning over, a "buzzing" sound is heard and everything else works.
Does this indicate needs new starter/alternator/ign switch???

2. 5th gear is slow. Gears 1-4 are fine. However, slow in 5th. When "Restore" additive is added pwr is gained back.
What/how can I do to resolve this?

All comments are greatly appreciated.

Well it depends on the buzzing. The starter relay may be failing. Or the starter solenoid has failed, where the starter spins free, but is not engaging the flywheel.

Badly corroded cables will make the car not turn over.

5th gear should not accelerate hard. There should be a noticable drop from 4th to 5th. Not to be confused with an acutal trans problem. A bad transmission gear is almost always very noisy.

buzzing sound?? hhmmm.. for how long?