What year did they go to a smaller upper radiator hose fitting?
 

I was hoping to install a 4 core radiator out of a '76 1/2 ton 2wd 454 truck into a '86 1 ton 4x4 454 with no problems, but it appears that the '76 upper and possibly lower hose fittings on the rad are different size. The rad in the '86 is only a 3 core...must have been replaced along the years. What year did this change happen? And is it both the upper and lower hose fittings that are different size or just the upper?