I haven't heard/seen anyone using the SSM stuff on the SHO yet but from my perspective I would go SSM over Livernois any day of the week.
SSM has been pretty big in the mustang V6 (3.8L) / F150 V6 (4.2L) world for a while. I talked to the owner extensively as I was working on build plans for my 03 and he is very knowledgeable and easy to talk to, and extremely responsive. I have a build 4.3L stroker from them (albiet used - about 1k miles when I bought it) for my mustang turbo build. The engine with turbo cams, made ~330 rwhp, without the blower, came close to 400rwhp with 6psi so I am looking to make 450-500rwhp with 10-15psi on my set up.
I would reach out to them and ask any questions you have, they are super easy to deal with IMO.