You know, I've tried to visit that link, but it isn't working on my computer tonight. I'll try again later.
Being a kit car, I believe it could have had just about anything under the hood. But the quote below is from a website that seems knowledgable.
"The S-1 had a wheelbase of 99", using a shortened early Ford frame. 'me running gear consisted of a new Studebaker V-8 engine with Edmonds two carburetor aluminum manifold. 3/4 race cam, domed pistons and dual exhaust. Couple that with a body that weighs next to nothinT and a quick shift standard gear box an look out!"
Read this fascinating article about the fastest one ever put together (with reference to shelby):
http://www.palitem.com/news/stories/...ews/80319.html