We have done a few of these, the older ford trucks always seem to break the ears off. As with anyhting cast, it is very prone to having porus surface and be full of oil and such. I always heat the area up with Oxy-fuel to 150-200F. You will be amazed of the oil that boils out at that temp!! Now that it's hot and the oil has burned away to just a residue, wire brush the heck out of it. Now weld it. It will flow like crap until you get enough good alloy into cast to make the arc stable. It usually takes all of 225-250 amps. I think your Miller can get the job done, but you do need a larger tungsten to run that amperage.