Can you see the curve of the walls?
Sprinters and ProMasters have nearly vertical walls, but Ford Econolines and Chevy vans, they have the curved walls. It doesn’t seem like that much of a curve when the van is empty, but oh it is! That curve is why I ended up settling on paneling for the walls. Paneling has quite a bit of flex and is inexpensive.
Even with all the flex though I ended up having to shim the top of the paneling in order to make it conform. I glued shims along the top and then screwed through them into the 1x2’s and 2x4. I used 1.5 sheets of paneling for the walls, the other half sheet I used later for cabinets. I measured and cut paneling in one piece for the long wall, this meant taking that sheet in and out of the van 6-8 times to make minor adjustments until it fit correctly.
The short passenger side was much easier:
I put some pegboard in at the rear of the van where the paneling ends to hang some things. Overall I am pleased with how it turned out.