Tires: tire size, gmc sprint, ss version

Question
what size tires came on a 1977 gmc sprint.  we are redoing one and want the right tires

Answer
Linda,

I could not find any reference to a GMC Sprint in my tire books, but I understand that a GMC Sprint was the same as an El Camino - and if that is true, a 1977 came with GR78-15's or HR78-15's, except for the SS version which came with GR70-15's.