I assume the relay provides both a hot/power lead and a ground lead (most relays provide both)?
If so, I bet the relay solved your dimness problem by providing a good/clean ground. Many years of oxidation/rusting/painting decreases/eliminates the good/original ground through the chassis and sheet-metal connections/grounding. Around 1955-2nd/1956 (I think), a ground wire was added/included in all lighting circuits.
Your solution is the best/easiest solution on our old trucks, unless we are doing a total restoration, where-in we can clean-up/shine-up and "protect" with antioxidant goop on all of the body/metal connections/paths from a good ground to the light housing-screws.
