Several others have already chimed in. Let me also say, YES. There is no reason you could not MIG weld and grind and have a VERY strong repair. Many years ago (40 or so), before stroker cranks were readily available, I read an article in a car magazine (with lots of pictures) about a company that built crank journals up with weld and then offset ground them to get the desired stroke. As long as you cleaned the parts up well and used a high enough setting to ensure good penetration, you should easily be able to fix them and have them looking good and be plenty strong. Post pictures when you are done.
