I've checked 2 different spec guides, 15" is the only listed option for the K10. 17.5' is listed for the K20. The 6 lug Budd wheel was used on IH, Dodge, and Ford 1 tons, perhaps Studebaker 1 tons, too. The bolt pattern is a very large 6 lug, not interchangeable with GM 6 lug.
What does your truck have on it now?