Welcome to the 'bolt. There's a lot of information and advice to be had here.
Try the links page (above) and the American Classics ad at the top. A lot of the parts are interchangable (particularly the body parts) but some are specific to the 3800. Jim Carter and Classic Parts of America (
http://www.classicparts.com/ - what was Chevy Duty) have a lot. There are a lot of others as well. And have fun with it.
But there is one question I have; Where are the pictures at? We all like pictures. Pictures are good.