body panels for a 48 chevy (not fleetside)?

You'll need to know what it is before you can search for body parts. The 48 Chevys I am familiar with have the front fender shape extend about a third back over the front door, but none "that run all the way back to the rear fenders." I suspect yours may be custom if they extend farther, and they car was also a custom with a chopped top. Maybe you can post a picture and give people a URL to see the car to help identify it. There are very few suppliers or replacement body parts for that vintage Chevy. You better identify what panels you want replacements for. If you are looking for patch panels, or full parts such as fenders or doors.