You can use the fiberglass gauze and patch stuff, but it probably won't hold
up too long depending on where you live.  Metal is better, even if it might
not be completely original.  I just had some Swedish repair panels welded
into my '73, but they didn't fit too well and had to be reworked quite a bit.
 I got them from JC Whitney, so it's sort of my own fault!  Anyway, I've
heard that Rocky Mountain Motorworks makes a good quality repair panel -
check 'em out!

jasons1390@aol.com