Well, the 87 TRX350 wiring harness does not have provisions for the TRX350D fuel sending unit or the LED fuel gauge. You can't just replace your wiring harness with a used one from a 350D Foreman either, cause there are other several other electrical component differences between those two models... even the stator is different... so its a cost prohibitive idea to attempt a harness swap.
Your only option is to add the necessary wiring for the fuel sending unit and fuel gauge into your existing harness. You can do that if you have some decent soldering equipment, soldering supplies and a few male & female plugs to accomplish a professional plugs-right-in-to-existing-harness installation...?
Your only option is to add the necessary wiring for the fuel sending unit and fuel gauge into your existing harness. You can do that if you have some decent soldering equipment, soldering supplies and a few male & female plugs to accomplish a professional plugs-right-in-to-existing-harness installation...?