Yes, the large ones slide up from the bottom. The repros have a flange that is much more prominent so you may have to file the top curve so they can go on and still stay snug to the metalwork once they are on. They are held by the 3 bottom bolts. The tiny one is held on by the bottom-most bolt as well. I also drilled and tapped a hole up under the sill to hold the little ones up in place.
Because they are alumimium, they will get dinged with sand and stones. I had my new aluminium ones chromed 17 years ago with what they call dull chrome or satin finish chrome. They look just like aluminium with this satin finish. This surface resists the sand and small dings better because it is harder. I think they just buff the outside surfaces because mine are still shiny chrome inside. I can polish them and shine them up as often as I like. With the aluminium surface, you will soon shine off the anodised finish and then they will buff black and your polish rag will also turn black. I plan to do this again some day soon because after 17 years and 94,000 miles, the dings are getting to be noticable down near the bottom.