hi George, and welcome to the right page!!
those 17.5's could be correct for the years if ya got a 3/4T - I think width would be 5.5 for the AD years but maybe even 6 - there was also a 19.5" back then for the heavier duty trucks, and the bigger sizes were available as options
16" could be correct too, especially for a 1/2T, tho others here might know better what was the "standard equipment" for your year
Bill
