Glad to see new people starting to restore Olivers.  What is right for you to work on, will depend on your taste and interests.  Just my 2 cents worth, but a 70, or 66-77-88 make good learning experiences, if only for the availability of parts.  These models, or one of your own choosing, of high production models make parts availability better.  Also the newer models tend to be easier to get parts for also.  Hope this helps, Terry.