I was over at my neighbor's place picking up some concrete blocks he gave me and I noticed his Bucket w/ weld on grab hooks. He says it cost him less than $10 overall. I had him install the bucket on his 3320 w/ 300CX loader. Top hooks on the bucket were nice and snug, the same as my bucket to my 300CX on my 3720, which has no welding or hooks on it. I never asked him, but I am guessing he either just zapped them on real quick, or he preheated the steel flat bar that is welded on the bucket attach hook and then welded the hooks on.
He says its been on his 3320s bucket for about 7 years. I see lots of people welding and bolting on to the bucket top wall. I'm sure that fine and all, but this appears to be a slick way to do it. Kind of minimalist. In fact, this probably reinforces the bucket attach hooks even more.