Summit radiator SUM-380459

The old catalog dimensions could have been the core size. If the radiator is a crossflow and had a 22" core width that would make both tanks 3.5" wide each for a 29" overall width. And as far as the height being 1" overall taller could be the 1/2" each support at the top and bottom of the core. I am only guessing, but it is a possible reason why the dimesions are different.