There are resistor harnesses you can buy which work for an individual circuit(bulb). I used a pair of those for my tail lights, which is four resistors total for the two dual filament bulbs. They were convenient to mount, just two screws to run into the metal behind the lights, a few inches back. They are plug and play, plenty of wire. I did have one LED fail though from the end terminal corroding(heat and current). That's very odd to me, that a low current would still damage that large wire terminal steel on the back of the 3157 bulb. I can push it in or wiggle it and make it light up, but any slight movement causes the connection to be lost, so no light. I swapped in a yellow LED I hadn't used yet. Red clear or yellow look similar behind the red lens.
They do run as hot as the OEM bulbs did, so the bulbs are cooler, but the heat is still back there. It's better than stock, and I'll slowly figure out what LED bulbs have the ideal brightness for me. They make so many choices, it's not simple to just pick any one an know it'll be what you prefer.
I do wish something could be done elsewhere to reduce the current "capacity" of those circuits. I think the LED issue is that there is excess current ability in each circuit, so the LED is overpowered and they flicker. I'd hope the people who actively work with LED's would find a better solution than adding a resistor for each bulb circuit. I've got way more to do than to figure that out right now.
