Greetings Philshrider. To answer your main question in general have you checked out the buying guide sub forum
https://www.airforums.com/forums/f353/ . You should be able to pick out whats important to you. There are a lot of common situations no matter what the year.
Specific to the Argosy well there are metal and fiberglass endcaps to check the conditions on. The clear panoramic windows are also unique and are hard to replace. The gray tanks were not always present and their capacity so small that they might as well have not been there anyways. And there is the paint job.
As I am not a pro at this information you might want to take up an inspector in your area.
https://www.airforums.com/forums/members/list/ has a listing of those in your area and nothing beats a pair of knowledgeable eyes. Its an almost 50 year old trailer so unless you are really lucky, there will be something to address.
Hope it works out and you're able to jump right in and begin enjoying it.
Dave