I'll take some other pictures of the spring mounts tonight. They are mounted to a 'frame' that is 3 boards - very dense 1" beech. The boards are lap jointed at the corner (very strong). The vertical board is attached to the base with a block of wood and screws. The horizontal board is a attached to a small block that wraps around the back of the freezer and is mounted to the freezer with a screw into the hinge mount. (It will make more sense with pictures).
The other end of the spring is just screwed to the lid. I used some carpet tape to stick the boards to the side of the freezer, though that is not working well. The boards bow away from the freezer by maybe a 1/4". I may try to epoxy them to the side, but the framework is pretty stable as is.
As for the 80 lb rating, I really don't know if it is each or both. I think both. I could hardly compress them before they were mounted and actually thought they were too much, but they seem just right.
I weighed how much force I need to open the lid by standing on a scale and pushing the lid up. Came out to be about 70 pounds.