Don't worry the serial numbers on the carbs, I've never seen two with the same serial number on a common project.
What is important:
- the carbs are of the same type (which yours are)
- they are jetted similarly
- the jets are actually the size that is indicated (easy to ream them larger and to not "erase" markings or re-identify)
- Webers are tuned thoroughly
- engine is in good condition with valves set
- electrical system is in good condition and with correct components