Hi Dan,
I have the same thread chaser set. It seems to work well enough for home use.
The threads would probably be cleaner after running the bolt through a die. But I don't know if I would run a die over those threads. A die cuts off any metal which doesn't fit the thread profile leaving less of the thread present. Those bolts appear to have less thread already.
Have you looked at old seat belt bolts as an option? Or thought about locating a bushing that will fill the void? These pages may help:
http://www.hotrodhotline.com/md/lapbelt/
http://www.oerparts.com/shop/search/...%20belt%20bolt