I don't have a 53 Ford but, believe that bolt and spring is used to absorb vibration and slight radiator movement encountered when driving. It's like a shock absorber. I would just tighten it enough to compress the spring so that the threaded portion of the retaining nut is fully engaged and the spring is compressed just a little. You don't want to compress the spring too much or it will then be useless.
Frame and body panels are forgiving under torque twist, radiator forgives nothing. Fuel tank is mounted similarly for the same reason.