ATS just mounts the old style motor mount upside down to lower the motor, and should be able to be done with any of the alternatives, from what I can see. .
I have seen and tried the three above mentioned plates. In my 69 Camaro LS7 swap with stock front clip we ended up using ATS poly mounts with the Hooker plates, my Hooker Super Comp headers fit perfect without issues-once we moved the mount hats forward and down. Didn't have to dimple, grind or file. It also moved the heads a more comfortable distance from the firewall. ATS and Autocraft are the same, S&P has two different plates for different postions. My advice is to be prepared to experiment.