Bob, you're right. The Transformers movie truck is running aftermarket Peterbilt fiberglass fenders, and I think they are made by WTI. Though they are different from the stock Peterbilt fenders, they do still have the smaller innder fender radius, like the stock fenders do. Here is a link you can check out!
http://www.wti-fenders.com/classicff-pb379.htm