Date registered: Jan 2013
Vehicle: 90 350SDL, 98 S420, 97 SL500, 94 S420, past owner of W108/W112/W114/W123/W124/W126/W140 & W220 cars
Location: Tampa, FL
Mentioned: 8 Post(s)
Quoted: 605 Post(s)
Didn't you say they would flow test them?
That does help with some of the initial setup, however, they still won't be a "bolt up" replacement - you will have to go through the calibration procedure in the manual to set them up properly. Would they also perform final adjustments once on the car, or are you on your own once they leave their shop?
I have no way of knowing your abilities, but if one has a clean, well lighted work area with some basic hand tools, rebuilding these is not a major undertaking.
The worst part is cleaning them, but you can buy a bucket of carburetor cleaner to soak the bodies in and that will do most of the work. A good source of clean, dry compressed air is important as well, but in a pinch you could use "canned air" as well.
The most critical aspect of rebuilding these, or any carburetors for that matter, is paying close attention to the instructions and not skipping steps or cutting corners. If you can follow directions you should be fine.