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Step 2: Spec LED driver, take a look here https://www.digikey.ca/en/products/filter/power-management-pmic/led-drivers/745 - note that “linear” regulators are just fancy resistors, so they will not solve the heat issue.
Step 3: Implement LED driver in new light schematic. This is only really needed for the daytime running lights, so only focus on the “tub” lights. This is because the other lights, ex. turn signals, are not on for enough time for heat to be an issue.