In about 97, I bought a used fiberglass cap for my 96 F250 long bed. They were 11 or $1200 new, and I got it for 500 bucks. Then I took it to a buddy who painted it color match to my red truck for $150. And without properly maintaining the finish, it looked great up until a couple years ago when the clearcoat started to fade and peel a little bit.
I cruised YouTube and found this: I wet sanded the whole thing, good spots and bad spots, and then wiped it all down with alcohol to get any oil/grease off. There were a few little chips and scratches that I touched up with Rustoleum (sunrise red?), very close color match. I wet sand that too. Then I used gloss verathane in the rattle cans to put two coats on it. I was astounded at how good it came out, certainly in keeping with the rest of the finish on the truck which is very good cause I use it like a hammer, only when I need it. Good for another 25 years.
I picked up two aluminum cabs for $100 each when I was doing my search for all things to redo my trucks. The first one had the vent windows on the side, but they didn’t open. And I immediately found the second one which did have the windows that open up an out on the sides which I prefer. I did the Missing Linc with the light bar, and I don’t need either of the caps but I haven’t gotten around to getting rid of them yet! Another big downside to the aluminum caps Is the dent very easily. If an acorn falls on them, you get to dimple. If you bump the side with a ladder or such, could be bad, and it’s very hard to get it straight again.
I have a carport the whole length of my two wide by two deep garage. I rigged up four pulleys above each corner of the cap. When I want to take the cap off, I get in and use my legs and my back to pop the foam seal loose. I pick it up a couple inches to put a piece of 2 x 4 under all four corners. I made some crappy little brackets that looked like a “J,” that I could hook under each corner, and then pull the cap off from one point where the ropes all come together. You only have to pick it up about four or 5 inches to be able to drive out from underneath it. Installing it is just a reverse. I haven’t done it in quite a while, but I did it a half dozen times in the first 10 years I had the truck.