Is the housing material steel or aluminum? If it's aluminum I wouldn't use a wire brush.Too rough and you will gouge the aluminum. Use a green scrubbie pad. Steal it from the kitchen when no-one is looking. Make the mating surfaces shine like a new penny. spray a bit of aerosol copper coat on both sides of the paper gasket, homemade or otherwise, (a 38 cal. shell is good for punching bolt holes)and let it hang until it's tacky. Stick it to the housing and holds in place with the bolts.. I think you can handle the rest.

Jay

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1984 300D turbodiesel
1983 300TD