Your post brought back pleasant memories. I had a GS650G and loved it. It was comfortable, dependable, and fast enough for me-at the time. I have been looking at on-line parts diagrams for the bike and do not see any reference to points. I see what's called a signal generator, but it's not available as a replacement part. I would suggest contacting a Suzuki dealer's parts department, in the good old days there would be micro-fiche to look at.
I don't recall a 650GT. Unless the T meant model year 1981. I had a G-shaft drive, standard. There was also a GL-shaft drive, high bars, smaller gas tank, stepped seat, cruiser. And an E model, chain drive, sportier standard.
Good luck with your project.
Larry aka CharlieDog
Bristol, TN