Welcome Mike - you've definitely found the right place to gen up on all things GT40 as there's a load of great material on here and lots of very knowledgeable users.
Try to use the search function before you post what you think might be an obvious question but similarly do not be afraid to ask, you'll be sure to get an answer either way.
So, your friend's GT40, how was it? What make? what impressed you and why?