I'm helping my big brother on a 60 El Camino. He got the chassis done. Now is the hard part, finding quarter panels, and rockers. He found some rockers for a 60 Impala and said he could modify them to work for the El Camino. The car looks like it lived in a lake. Pretty messed up, but he is a pretty good metal worker. I told him I would see if someone hear could lead us in a direction to find some panels or someone who can make them or maybe a donor car before we attempt to fab some. Any help is always appreciated.
The ranchero seems like it would be an easier project but at least you are sticking to working on cool car based pickups.
Donor might be your best bet. Wagons. 4 doing sedans. Don't forget other GMs of the same Era. Buick, Pontiac, Olds.
If you are only trying to replace sections of the quarter you might try making templates of the curves you need and seeing what curves of other cars may fit. Did that for lower quarters on 66 Malibu. Who knew that the tops of 71/72 Malibu SW doors were the perfect fit.
I bought them from a place in Ohio. I know there is a picture in my build thread that shows the name of the place. They were 2dr panels, but the modification for them the work on the El Camino is simple.
I tried every vendor. And I mean every vendor. They all advertised the parts, but nobody actually had them. Told me I could pay and as soon as the came off of backorder they would be sent to me. I might have been born at night, but it wasn't last night. With the patch I showed you, or any impala patch, you have to move the "spear" that aligns behind the corner of the bumper forward. I'll see if I have a picture.