You didn't say what shape the shocks are in, but, if you think they might need replacement, the spring may be a moot point.
Since the spring is gone, you will have to take at least one end of the shock off to slip the spring off.
While you have the shock disconnected, run the shock in and out as hard as you can by hand. If there are any "soft" or "free" areas in the travel (particularly at the point where the shock normaly "sits"), it's time to reshock.
A worn shock absorber system will really affect the ride and steering. AS installed the springs on the shock to be neutral when sitting with a normal load, so the spring action really comes into play only on a "bounce" or return.
Several members of the Forum have reshocked with Gas piston Bilstein's. I have, and since the Bilstein's design does not permit the reinstallation of the springs, did not reinstall the springs.
The upward force the Bilstein shock exhibits at rest (gas piston effect) is around 80 lbs. I compressed the spring by hand, and discovered the amount of upward force contributed by the old shock spring was surprisingly low - I estimate around 200 lbs at max compression.
I am very happy with the new Bilsteins, but there are certainly other manufacturers of quality shocks out there.
If you prefer to go back with external springs, any shock mounted aftermarket spring should work (barring frame interference). You might have to purchase a pair to match them.
My opinion is that if the old shocks are more than a couple of years old, and considering the time and effort it takes to check the shock and respring, just plan on replacing both of the front shocks with a pair quality brand shocks. That way you know the history and one more portion of the equation is eliminated if you have to trace out squirrley handling, front end vibration, and abnormal tire wear.
"Suck it up, spend the bucks, do it right the first time."
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