Here is my opinion on it.
I'd clean it all up, use at least 1/16th tungsten or smaller and weld it up. I'm not sure how much I'd bevel it. Probably none because it's not that thick, if you have too much push through your going to have to clean that up. You definitely could weld the handle to the bolt also. It would make it much stronger.
It's really not that big of a deal if someone is proficient with a tig. A mill would def make clean up easier. Baldwin Gun Works could fix this I'm sure. I really dont have time to mess with it, but if you cant get anyone else send me a PM I'll hook you up