Where is the VIN?

[TeamDar]

I would say it is a 1978 GS750C. That is the correct color. If it has the choke lever on the carbs it is a 78. If the choke is a push-pull on the steering stem then it's a 79.

[recycled64]

The ignition key placement/steering lock arrangement is always the most telling difference between 77-78 GS750. Tanks and plastics can be changed, etc, but ignition switch location difference requires too much 'modification' for a 77 to morph into a 78. So-78 it is, and a nice looking one at that!