I believe some of our vendors still sell the Fridgette kit. My 66' 230SL had the original Khulmiester, it even has a cool little Khulmiester decal on the hardtop window. That older system was pulled out in the eighties I think on my car and was replaced with a Buds Benz Fridgette. It took a little work to get it working really great. It took about 5 hours of pulling a vacuum on the system while heating the accumulator and recharging with some good ole R12 I found on Ebay. I had to spend a lot of time remounting the condenser in front of the radiator. My car still has the old condenser that was mounted behind the front bumper and is about 5" square and about 30" long. From reading on this site the old compressors would sometimes break the pulley off the front of the crank on 230SL's. So watch out for that and do some searching here to confirm my memory. I would like to put the old Khulmiester evaporator under the dash and use the modern compressor. The Khulmiester unit looks really cool and better than the new Fridgette in my opinion.
So, I think you need to know what components are in the car and be prepared to do some work. You can also just buy the kit and install it on any W113. I do highly recommend the system. It is really "cool" to ride around in the rain with the AC going on a hot day. I don't know how it would work in the hot sun with the top up, we don't get those in Upstate New York.