Do a search here with Saiga as the keyword and nalioth as the username...there are a few posts of his that might help. Alternatively, PM him (nalioth) with any questions, he's a Saiga "expert."
They come optics-ready with a side-mount plate. Another option if you want to run a red dot or holo sight is to get an Ultimak rail (about $100) that replaces your gas tube.