Hi 9shooter,
E6011 is usually used on rusty material and pipe. E6013 is an all purpose, general repair electrode. The main difference between the two from a manufacturing standpoint is in the coating.
9shooter,
We always just used 7018 on anything like that and never had any problem. Just make sure you don't heat the scraper blade too much (you don't want the whole thing blued) or else you will lose the hardness necessary for wear resistance. These things are expected to be replaced, so its not really a rocket science and you don't have to have any "special" rod. Be sure to clean the dirt off with a brush and slap the thing on. I will almost bet that the original blade was welded on with a mild steel filler, and if you are replacing due to wear, obviously the weld doesn't see near as much wear as the front of the blade, so don't spend extra money on wear-resistant welding when its not necessary. A stainless root, I think, would be shooting yourself in the foot, as its purpose in this application would be wear resistance, and putting it at the root, then burning over it with 6011 would gain nothing. If anything, 6011 root and stainless cap for wear.
Hope that helps!
G. L.