I love these old Zenith portholes. The back cover on mine bulges out about 2" to protect the CRT.
Here is what the back of mine looks like:
http://www.cerant.com/ZenithTV/BackV...overOn-800.JPG
Make sure all the mounting screws are in place holding down the Main Chassis and the Power Supply chassis. You don't want a chassis flopping around during shipment. Also, make sure the wood shelf those chassis's sit on are not loose.
Nice to see someone here purchasing that TV. Post some pictures and keep us informed of your restoration process.
Carl