My name is Dale.
Would you mind telling me what you kneed to know about the rear deck springs? It is my understanding that the key or trick is to strectch the spring and then figure a way to hold it in that position and insert it with the deck partially closed and then close the lid and allow the spring to compress. Here is one Corvette technicians discription of how he does it.
I'd stretch the spring. Then get a bunch of wood wedges and insert them in the spring to keep it stretched. Install the spring. When the lid is closed, the wedges should fall out...
There is a special tool made by Kent-Moore to do this operation. The Tool # XXXXX: J-9559
Did the information I researched and provided for you help you resolve the issue? If so I would appreciate it if you would accept my answer so I get paid for my work.