1968 Plymouth Barracuda Fastback
I can't really tell all that well, but it's either 7/16", or 1/2".
The trim is a little 90* piece of steel, countersunk for the screws. You could probably get something like that at home depot or on amazon. It's about 1/2" on a side. I suspect that I'm going to replace my plywood separator with something hopefully lighter.