Ya know Stick Welder, when I first read your response I kinda thought you were being a weld snob but after just a bit of thought I came to the point that you are right. We dont know if the guy can weld or place chicken scratch"ens and (no offence intended to the OP) that he had to ask what rod to use lends me towards #2.
If you decide to weld those hooks on the bucket please go find something that there is no way the tractor can lift it and hook a chain to it for a test. Years of being around such has taught me that no matter the intended use, eventually something real heavy will be attempted. If it breaks you want it to happen under controlled conditions, not when something valued is being lifted or when a person"s life could be in jeopardy. Safety freak? nope, just a realist.