i want to buy some rear calipers but since im short on money im going to rebuild my seized ones instead...........i went to rockauto.com and they had many different types for sale....different bore sizes ect....which is the size for my 85 gsl calipers (rear)

 

Looks like the rears are 35mm bore... which converts to 1.377 inches or 1 3/8. So either the 35mm or 1 3/8 will work.