Oh wow, I guess I forgot (or didn't think, much more common) to take a picture and post the specs on the bolts I used. I got the correct bolts from Fastenal. The repair kit did have 4 new bolts in it. But, they were too short for my application. I think you want to use a bolt called a "shoulder bolt." I'll try to post a picture of one that I just grabbed off a site:
I tried using the ones that Liftco sent me but when I got them tightened down it was clearly causing that threaded rod to bend and bind. I think you want the bolts tight against that shoulder and plate. And you want that threaded block to float on the bolts as the rod is turning throughout it's travel. I'll try to remember to look and see if I saved the receipt for the bolts to tell you what the specs were on the ones I got.
As far as trying to fix what you've got, or buy their plates. I think I would just buy their plates. They weren't very expensive if I remember right. Maybe $25 for the pair? I drilled several holes in them and then used self tapping screws to bolt them down to the original metal plate there. The thing about doing it this way is that if they break again it should be pretty easy to fix. I used anti seize on the threads of the shoulder bolts. I also coated the shoulder part with anti seize to hopefully make it so the threaded blocks slide up and down on the shoulders as the slide is moving.