If the part number is different, you cannot risk it. The same motor can have massively different mounting points for all kinds of things.
Be especially careful with AC. You want a shop that knows what they are doing. Get it wrong and you can hose the rest of the system. foul the receiver drier, or damage the evap.
If all you need is 4 months (and you are SURE) buy a junked one.
Keep it as simple as possible...but no simpler.