Walk in the park, since all you need to do is clean up the taper in the tang, then start with an over size head bolt to lathe taper it down to match the taper in the channel. Also, since this is going to be a shooter, start with a over size allen socket bolt, instead of a slotted flat head screw that will just get buggered up instead.
And truth me, there is enough width of the tang if it the taper has to be made slightly over size of the standard bolt head if the taper channel was over drilled, to save from having to weld, and re-due the taper back to factory for a factor bolt.
So we clean up the tang tamper, lathe a bolt head to match the tamper of the tang, then just shorten the bolt as needed. A quick clean and cold bluing of the bolt, and all is right again with the world.