i have some rust on the lower part of the inner & outer wheelhouse (rear) about 5 inches, where can i get a patch panel. 70 chevelle

I've not seen a patch panel for the outer, the whole thing is about $65 and pretty easy to replace. A patch is available for the inner one, I think Year One has them. I bought mine from Chevy Restoration World in Ohio (937) 236-5233 for around $40.