Why not contact XS direcectly? Here is their URL:
http://www.xssights.com/ What you have on the Marlin are just the filler screws, and you will probably have to spring for screws with heads on them from your local gunsmith, unless XS will pop some in the mail for you.
Depending on what they want for the AO sights, you might also want to check out Williams peep sights. Their WGRS mounts like the Ashley and is plenty rugged for a bunch less money. If you want the "ghost ring" you just unscrew the aperture. When you sight it in and want a fine sight, you put the aperture back in.
-WH-