Anyone that says a 26” radiator behind a 22” radiator support isn’t much benefit doesn’t know what they’re talking about.
The amount of the 26” core that’s obstructed by the slightly smaller opening is pretty minimal. It’s true, the cars that originally came with 26” radiators had a larger opening in the support, but the difference isn’t that much. And it’s not like the core is pressed against the support either, the extra core that’s “behind” the support opening still is exposed to air, so it still works to dissipate more heat than the smaller core.
And more importantly, when does the car run hottest? The biggest cooling issues with these cars are usually at idle or slow speed, when the fan is doing all the work of moving air. If the fan is doing the work, and you’re running the proper fan shroud on the radiator, the fan will pull air across the entire core. By not opening up the radiator support to the full core width all you do is obstruct a little bit of the core when the car is moving at speed, when the speed of the car is pushing air through the grille and the radiator opening. These cars usually don’t have any issue cooling at speed.
My ‘74 came with a 22” radiator, I run a 26” now with an electric fan set up and the original radiator support opening. At speed my fans never run. At all. The smaller opening moves more than enough air at speed to cool the car to the thermostat temp. And at low speed or idle the fans pull air across the entire 26” core because of the 26” wide shroud.
You will have to add the mounting points for the 26” radiator if the car was set up for the 22” because the mounts for the 26” radiator are wider, but that’s all you need to do. Opening up the hole in the radiator support will help move more air at speed, but it’s a small difference.
This is a picture of the 22” radiator support in my car with the 26” radiator, the mounts for both radiators are marked, as well as the full width opening for the 26” radiator support…
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And this is a factory 26” support
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