I just replaced my lower control arms on my '87 300D. You ABSOLUTELY need to use a spring compressor if you plan on letting the control arm drop. The spring expands too far and therefore the angle becomes too great to recompress the spring without the compressor. You may be able to put a jack under the control arm to hold it enough, to just replace the strut, but I would think that would be pretty risky and you definitly can't replace the springs without one.

I used a set of spring compressors I had for normal struts that mount on the outside of the spring, and I almost couldn't get it back together because the spring started bowing out. I ended up having to loosen the compressors a bit to get rid of the bow, connected the lower ball joint, then setting the spring on the control arm I had to connect a come-along to the arm and pull it toward the other side to get the bushings to line up, while using a jack underneath the control arm to recompress the spring the rest of the way.

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