Thanks for sharing. These are truely great bikes, and largely overlooked because it seems everyone wants a CB750, XS650, or KZsomethingorother. Pluse the GS bikes are better handling because of better bushings in the swingarms and roller-bearings on the crankshaft that make the engines nearly indestructable.
I highly recommend you join the GS Resources forum. Lots of GS crazy-knowledgeable peeps there including me.
Here are some pix of a '78 GS750E that I rebuilt about this time last year and sold to a collector in Japan.
I still have some NOS parts for the GS750 that I never used that I'm sure would do you some good, like intake rubbers, NOS badges, some brake/clutch cables, etc. Give me a ring or shoot me a PM if you need any help or advice.