Brian,
Wecome to the fraternity. Your car is beautiful. I know you are excited and will be pleased with your wise choices.
Evidently the 427 SRX is so new Roush doesn't list it on their web site.
Are you sure about the "X" ? ... or maybe Roush is making one especially for SPF?
From the numbers you give it sounds like a 427 SR.
Take a peek at the website and see if one of those listed fit yours.
http://www.roushperformance.com/engines/engines.shtml
Jody