Air box is open topped, there should be a perforated plate, a flat foam filter and a wire spring thing to hold them down. The seat base should be glass fiber and wood. But they do look like they are home made. Don't bother with getting the triangular silencer they make the bike run like sh-t.To much back pressure! I'm at sea at the moment but will be home at the weekend. I will take some photos of the side stand and the old foot pegs that I have in the work shop.
P M me your email address if you wish and I can send you photos direct. Have you had a look at the photos I have in the add? my bike started out in about the same state as your's