Put a Champion 526 radiator in a 71 swinger?

Somehow your pictures aren't showing.

Your car has an identical radiator support to ours. All 67-76 A-bodies can handle this radiator width wise.

I went out and quick eyeballed mine. The width of the tank section is 27". The width of the edge of the brackets which are all above the inner fenders is 29 1/4"

If I measured at the center of the radiator support on the engine side to where the edge of the tank is on the engine side is 4". The actual fins on the radiator are 1/2" farther set in. They are correct with the actual thickness being 2 3/4" at the tank.

Sounds like it will fit well to me.

I have a "Chevy" Alternator too. 78a 12SI Delco.

This is kind of a fuzzy picture when I had my old engine (hadn't been pulled yet) and I was mocking it up. Maybe this paints a better picture? The contour fans are 3.3" thick from the core to the back of the fan motors.