A K-30 came stock with a 60 front, but usually the 14 bolt GM axle in the rear. Ford and Dodge used the 70 rear, with Ford later coming out with a 10.25 inch axle of their own. Look under your truck, is the axle straight, and using leaf springs? It cannot be IFS with a 60. Dana never offered anything like that. On older Ford 3/4 tons, they did nake IFS 44's and 50's, but not 60's. And certainly not Chevy's.
'79 GMC shortbed 454 th400 14 bolt FF NP205 Dana 60