Front springs are not body style a specific. There are a few variations according to the engine and trim.
You want a standard V6 front spring. More specifically you need 2 and unless they were recently changed, you would be well advised to do the front struts and wishbones. Haters will always hate, but this is what I fitted to my own Omegas and several for other people. It's not cheap, but it's a they only way to do it properly. The only thing not on the list is the Power flex front wishbone bushes. I would but you might choose not to.
Front shocks
https://www.ebay.co.uk/itm/303900706727Bump stop
https://www.ebay.co.uk/itm/389407894145Top mounts
https://www.ebay.co.uk/itm/267520937164Front springs
https://www.ebay.co.uk/itm/126057776492Wishbones
https://www.ebay.co.uk/itm/388331065649Rear end:
Rear springs
https://www.ebay.co.uk/itm/286902588255Rear shocks
https://www.ebay.co.uk/itm/389362518864Rear track rods x2
https://www.ebay.co.uk/itm/365676388824It's a days work on the drive, but a garage should be able to smash it out in a morning.
Once done it will need the alignment doing properly or you'll destroy tyres and hate the car for the way it drives.
Geometry settings are readily available on here but basically front toe (in) -0°03", front camber -1°10", and thrust angle 0° and not a second off.
When you add it all up, it's not a cheap exercise, but by the time you've taken the strut off to replace the spring and refitted everything and done the alignment, you may as well have done the lot. Notwithstanding the fact that only replacing one spring is the definition of retarded and dangerous, not to mention criminal.
All of that and it will drive like a brand new car.