I was recently given a Ruger Mark 1 It is in good condition overall, but is missing a rear sight. I have done some looking online, but most of the sights I am seeing are for the Mark 2 & 3. I was hoping to get answers to several questions. Are the rear sights for the Mark 1 & 2 interchangeable? Since i already need to replace it, any upgrade to the sight i should consider? Lastly, any recommendations on reputable dealers to get the sight from? Any help is greatly appreciated. Now off to find magazines!