Inorder to get EG shocks to fit into an EK the fronts work without any problem as they are the same.
The rear shocks however are different on how it mounts on the EK. EG arm bushings are longer which is true, but the distance from the top of the arm to the middle of the bushing is also shorter since the arms are cast.
EK arms on the other hand are pressed steel, first difference is the shorter shock mount bushing and yes you can add washers to make it work. However one thing that no one bothered to mention is that when you mount the EG shock onto the EK arm you will find that in order to make it you have to jack up the arm because the bottom portion on the EG shock is shorter which binds with the EK arm.
Does it work of cause but if you jack up the car the shock will hit the arm acting as a limitter which can be a bad thing or good depending on the situations.
How I know because I am using it on my EK, I cut part of the shock mount off to allow for a bit more travel. It works but thought you should know.
And to make EK shocks to fit the EG I would not suggest grinding the bushing as this creates trememdous heat which will damage the rubber part of the bushing. You can widen it by taking the 32mm axle nut and hammering it wider then compress it to fit the bushing which would also work. Did this on my CRX before, good luck. You might blow out your shock if you slam your car since the EK shock is a bit taller.