Truck questions
Clint,
Factory replacement wires will be all you need if you're not running an aftermarket ignition. Stay away from the Autolite replacement wires as they tend to stick on the plug and break. Champion makes a "Truck Plug" that has worked just fine for me on all my Dodge trucks. As far as motor oil is concerned, standard Valvoline 10-40 or 10-30 should work just fine. Your truck has a roller cam from the factory, so you don't have to worry about Zinc based additives. If you wanted, you switch to a synthetic like Royal Purple, but they're really expensive and be sure you don't have any seal leaks or the syntetic oils will exagerate the problem.
As everyone else said, 200 degrees isn't a problem on a modern fuel injected engine. They are set up this way from the factory to increase mileage, decrease emissions and reduce cylinder wear. If you were to add an aftermarket performance computer, they usually recommend installing a 180 degree stat, but I would not reccomend it on your stock engine.
As far as the clunk is concerned, I would check your U-Joints first for play. When the tranny is cold the oil viscosity is high and could be transmitting some torque to the driveline even thought the trans is in nuetral. When you push in the clutch, you remove any source of torque from the tranny input shaft and the driveline relaxes. If you have play in u-joints, you'll hear a clunk. If you have no leaky seals in the tranny, I would definitely recommend changing the fluid and using a synthetic.
That rear end howl is bad. Hopefully it's not a pinion bearing. You can change the fluid but I'm doubting that will cure the problem.
Hope this helps.