Bad connections, especially grounds in these trucks as Chargerx3 has pointed out, are the primary culprit for electrical gremlins. Honestly, disconnect all of the grounds on the block, frame and anywhere else you can get to them, give the grounding loops a good clean with steel wool and even take a wire wheel to the bolts to de-crud them before reinstalling. Check the ground cables are still in solid condition with no swelling or split insulation. Using LED's are a great idea - they take a load off the electrical system and are way more efficient If you're going to experience electrical problems, it will be at night when it's raining and cold. Lights are on, wipers are going like your life depends on it and the heater is trying to stop your windscreen from turning into a sheet of frosted glass. IMO you shouldn't need to go any bigger than a 90amp alternator. Add to it a battery with a good CCA rating like 660 or better - the biggest 12v battery you can stuff in there like a 13 plate. Guaranteed you will never suffer from sluggish starts or accessory issues. Add terminal grease to the battery poles - and please use a proper battery clamp and not an elastic strap. If the positive terminal hits the hood you will know straight away + the LEO's may not like seeing that on a roadside check...