Radiator options for cooling a 6.0 swap in a truck that runs hot — 27-inch vs 34-inch?

We haven't verified which size fits your truck's core support, so measure the opening (height, width and thickness).

What Speedway says about sizing:

• More core area and more rows mean more capacity: a 2-row is worthwhile even for stock engines, and 4-row suits towing and big power.
• More rows isn't always better: each row adds thickness (measure the space, including fans and shroud — thick cores have hit pulleys and steering boxes), and a thicker core is more restrictive to airflow, so the rear rows do less and the fans work harder. You reach diminishing returns.
• A shroud that covers the whole core matters. A wider radiator only helps if the fan and shroud pull air through all of it.

Also rule out the tune and water pump if it runs hot at speed: a lean air/fuel mixture makes cylinders run hotter, and ignition timing that's too far advanced or too retarded also adds heat. Speedway notes improper timing or air/fuel can make an engine run hot even with a properly sized cooling system.