I am having trouble determining which of the 1978 gs1000 Suzukis I own. The dealership can only go back 10 years with vin#. I understand there are the gs1000,gs1000c,& a gs1000cs models made in 78.The master cylinders look the same but have diferent diameter pistons and cups I ordered the parts for a gs1000c. Wrong part ($50.00)shot. My bike came stock in the blue color with black & white striping.If you know please help me figure this out. So far Ive been unable to get an answer from local shops or Suzuki. Thanks much.