Some considerations.
Trying to find a phase 1 Ac system for a 107 may be difficult. Finding one that is the phase 3 system (automatic) will be easy. I know of a couple here in the DFW area at junk dealers.
The problem with the auto system is the vacuum elements inside the evaporator box. You will need that box from a donar car. While it is out I would replace all the elements and reinforce the inside element base to prevent the box from breaking. Now the majority of your potention problems that the older 560SLs are facing are solved. Wood trim is available, new or old. Parts etc. So I would consider a 560SL donor. The system is morecomplicated but you will have to learn A system. So you might as well learn the phase 3 system of the automatic AC system.
Don't get the phase 2 AC system. Parts availability problems.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car