I tried this swap as I had read that you can do it. My experience was that after drilling the 5th hole things still didn't line up perfect. I would think that you would have to use all of the brake hardware that came with the 7 1/4 plates in any case.
If you are interested I have a set of used backing plates and new drums and shoes for an 8 3/4. The drums are drilled for 4" and 4 1/2" bolt patterns.
Jack