Yes, the seat springs also fit on a Deere X485 seat. However, the installation procedure is a bit different. Since the pivot points on the X485 are welded together, there is no simple way to disassemble the suspension. So instead, I used a pry bar and a large screwdriver to compress and then pop the springs out of the lower pilot, and then took each, one at a time, out of the suspension unit. Putting the new springs back into the suspension unit took maybe a minute longer than taking them out, but the entire process was a 10 minute job max.
The best part? Mrs. N loves the ride with the new springs. It made a big difference in ride quality. Thanks KennyD and psrumors!