Most NEMA design motors are rated for -10% of nameplate voltage, so you should be OK applying 208V to that motor. But if the line drops too much lower than that, i.e. 200V, you are pushing it. You will also have a loss in starting torque and higher current draw when running, but that may or may not be a problem. You can't really tell until you hook it up and try.
The thing I would do is hook it up as is, and if it starts successfully, run the compressor continuously for 10 or 15 minutes by opening the bleed valve, and monitor the motor current. If it climbs up into the service factor amps, let the customer know that this will shorten the motor's life. Chances are that the motor was a little oversized to begin with, so it may be just fine.