Jay, I also had a 70's GS550 (my last bike actually) and it was a superb cruiser for our narrow, twisty Cornish country lanes. Had Givi panniers plus topbox and went camping two up all over on that bike. I put braided brake hose on it plus had made stainless steel brake pistons front and back, a massive improvement.
They say the GS550 was the most bomb-proof bike ever made in Japan. Gear primary drive, roller bearing crank etc, those engines were indestructible!
The GS650 shaftie was quite the opposite. Famous for failing camshaft bearings, mine failed right in the middle of the huge Orwell Bridge in Suffolk on my way to the Isle Of Man TT ?
Regards,
Jay.?