Best way to get a Roush engine is to make sure someone else builds it, and then put their valve covers on it.
Even at $1000 a pop for vavle covers you'd still come out a head $$$ and have an engine that works.
PS: Welcome to the forum... I bet you never thought that you'd have opened a can of worms with your first post did ya? Enjoy... and congrats on the SPF - great cars!