Mac's Antique Ford Parts has most panels for most old Fords. Don't know much about their quality but if you're asking they are probably in better shape than the ones you have! Do a search on Google or something and when you get to their page look to the right side and browse online. Their search engine works pretty well, usually.
I make a few 49-51 sheetmetal panels. You can check out my parts at http://www.nicholsonrestoration.com/shoeboxfordcatalog.htm. I'm also a dealer for Macs.
for 49-51 ford shoebaox try emsautomotive 216-541-4585 or www.emsautomotive.com, mac's sells there parts and yogi's too
Do a search on the HAMB before purchasing EMS panels. They require lots of work to get to fit. I would use them only as a last resort. They basically make a good starting point. I am currently working on a '49 Ford for my dad. I ordered inner and outer rockers for it. The outer rockers were pretty much gone. The EMS panels are requiring a ton of work to get to fit. The edge where it meets the door isn't sharp enough so its about 1/4" low. So I am having to reshape the edge to get it to match the door. The EMS inner rockers are universal. I decided not to use them and repair the originals.
you will find our parts to be of superior quality, all parts leaving our factory are lableled unforuntatly some folks try to p*** off inferior parts as ours (ems automotive) look for the label or call us to verify dealer is authorized by use as a reseller, our web site has full photos, and parts availbilty list. listed in the links section is online resellers www.emsautomotive.com