I have recently replaced several panels in my '51 3100, floor pans, inner and outer cowl panels, inner and outer cab corners, and I can assure you the replacement panels have probably not improved significantly since 2006/2007. Just about every panel required some tweeking, some more than others, so you can expect this. I got my panels from LMC Truck and Brother's Truck Parts, so I can't speak for others, but I have heard some say they all come from the same place - China! Good luck, take your time and don't get frustrated!!
