Have you thought about aluminum brazing in all the pits and the crack? Much less heat than welding (700*-750*) so zero warping and nearly as strong. MAP gas torch and your all set. Hobart makes good rods #770206. You could then grind it smooth and nobody would be the wiser. Lots of spots on my DR were done this way. The color is a bit off as the Al brazing rods are a different elemental make up to make them melt lower than the base metal so polishing would be a no go but with a brush finish nearly nobody could tell if you didn't point it out. Give it a try and if it does not work for you you can still cut it all out.