Stupid Radiator hose fit question

[oteixeira]

OK, so I swapped in a 5.3 and now I can't figure out the radiator hose to buy on the low end. I hand measured, and the inside diameter of the 5.3 hose seems to be 1.5 inches, the diameter of the radiator is 1.25 inches. I thought I was set, found a bunch of hoses, then I went to double check, and rock auto and other retailers online say my hose (for the radiator of a 1970 C-20) should be 1 3/4, and that would be way to big. Are my measurements not where they should be taken? Should I have done outside diameter ? I don't want to buy a hose just to chuck it away.

Thanks in advance,

Orlando