This engine is a 460 swapped into an F-100 that the owner had some pretty serious valve train problems with. The engine would randomly toss the push rods out of the rocker arms. New correct length push rods and careful attention to the rockers geometry fixed this concern.
Anytime anything in the engines upper end is replaced its a necessity to pay attention to the valve train if you want the engine to stay together. Luckily this didn’t cause a complete engine failure.