I don't think what you're looking for exists. If they did, the would be preferred to air shocks. You can convert to a coilover system, but it will require more than simply removing your shocks and installing adjustable coilovers in their place.

I put new gas rear shocks on my 59 Edsel Ranger but would like to upgrade to an adjustable coil over shock.  The car is original and has stem mounts for the shocks - top and bottom.  I'm having trouble finding stem mount coil overs.  All the ones I'm seeing have at least one (usually both) through bolt (eye) mount.

I have found stem to eye adapters but they don't seem ideal to me.  I'm not sure they are secure enough and as each mount adds an inch or 2 to the mount point they limit the amount of travel.
Has anyone used the adapters and if so how did they work?
Anyone know if there are coil overs with stem mounts top and bottom that would boil directly in and work?

John