I heard that the floors, trunk, and roof panel ane the same for most a-bodys. Is this true and are there any other parts that are universal...

That's an open ended question that can't really be answered...;). Many parts are the same and many are year specific. I think a lot of the under body parts are the same from '69 to '72 including floor pans and body bushings.Many upperbody parts do not interchange and the interior parts are year specific in many cases. The parts vendors on this site and others will be very helpful in making your selections. I would call and check before ordering....:beers:.
You are now in charge of the research to make this list....:D.

Good luck in your search and if you have specific questions, ask and you will surely get an answer here..........:thumbsup:.

The way the title is phrased it sounds like you are asking us the question if we need in and you are offering the information.
I am fairly certain that there is a parts compatibility index somewhere, though I forget the name.
Tires, gas, and floor mats should switch out fairly easily. But seriously if you ask about specifics someone will know.