If you can get some I'd say they'd be great - I know much swapping has gone on with springs between Carlton and Omega (or, if you're German - 'Omega und Omega') and such as Lotus Carlton bits where they have become unavailable/unobtainable, the Omega has provided parts.
Bear in mind there is a weight difference, not sure how much between an evo500 and an Omega. That said a 2.0 GLS and a 3.2 Elite weight about 150kg apart (or some similar figure) and they share springs, so shouldn't be a massive issue. Just imagine the difference between and empty car, compared with a car with 5 fat people, their luggage, plus a full 75 litres of fuel weigh, you get the idea of how much weight the springs take without significant alteration of ride height/handling.

Apologies, but I beg to differ... different models with different engines will have different spring rates... look at the choice of Irmscher springs for the Vectra C as an example... different spring rates front and rear according to engine AND body style.
Iirc, there's about 20% difference between the front axle weights of the lightest models vs the heaviest ones.
Fit too light a spring and use the car for towing/family holidays/hooning around and it will be bouncy, handling like a badly set up Elite on 200k mile shocks, will eat shocks and likely break the springs in short order.
Fit too heavy duty springs, then the ride will be crashy and become prone to throwing the back end out at the fist sign of a damp corner...
Lowering any given car/model requires the correct length and correct weight spring... fitting any old spring from summat vaguely similar is a quick and effective route to a Darwin award
