Bench to bucket conversion, need help please

I think the seat braces they are referring to are the reinforcing plates welded to the floor. They are nothing but 1/8" flat stock around 4 x 4 with a hole thru them for the seat mounting stud.
Those factory dimples work if you are using a stock A body seat with stock seat tracks, but if you are using an aftermarket seat, the width between the tracks is probably not the same as a factory deal. Therefore, I would NOT rely on the factory dimples to mount your seats. Otherwise the factory holes might not line up with your track widths. I went thru this trying to use B body seats in an A body. I would get your seat to line up as best you can side to side and front to back and make new holes, then make your own reinforcing plates and weld them at each of the holes you make for your seat tracks. Then cover the old holes with either plugs or weld some scraps over them. Center punch your intended holes first and check the underside so the holes, drill bit and bolts won't interfere with anything.