The only component I see of value in the photo you displayed is the air plenum with the vents that mounts under the dash. If the evaporator core is solid you can still use that. The compressor is R-12 and the condensors are the old serpentine type. Don't bother reusing those. You should also replace the blower, hoses get replaced with barrier type for R-134, New Sanden Compressor and of course the parallel flow condenser. Also replace the dryer at the firewall. Once the dryer is exposed to the air for extended period of time, its internals no longer do their job. You will also need the appropriate compressor mounting bracket and pully's. Joe Alexander reviewed on this forum an improved setup using 280SE A/C components. You would be looking for the compressor mounting bracket (photo attached), engine pully and the top of the thermostat housing (Which has a taller neck). Another issue to consider and prepare for is the added stress stress to the engine resulting in increased operating temperatures. 280SL's can be particularly vulnerable. Others have added electric fans at the radiator, heater core bypass lines, and even electric water pumps and radiators with better heat dissipation efficiency.
You can also find the Fridgeking installation manual on ebay by searching "Mercedes 230SL AIR CONDITIONING INSTALL - SPARE PARTS - SERVICE MANUAL". The listing shows several photos of the manual and will give you a good idea of what is involved.