They are different. 6501 charge units are designed to use a height adjuster (to help eliminate uneven prints). I don`t know if they are compatable with each other, Ive never tried fitting a 6500 corona into a 6501 (or vice versa). If anyone has tried and results are ok please let me know so I can reduce my car stock !!!!
Part numbers are A0UR71200 = 6501, A03UR70300 = 6500. Cheers
