9" drum to disc conversion confusion

I am doing an 8 cyl swap also. I was looking into converting the brakes. I found a 9" option. Scarebird has a kit that uses Toyota Previa rotors and they include a backplate. You just have to buy Chevy celebrity calipers and pads and a Caddy hose. It is all in the setup specs. https://scarebird.com/

They will be installed pretty soon. The engine is already in, just needs to get it running.