67 front left axle

[walt7860]

i hope i can get some help iam replacing the front drive axle. i went to oreilly autoparts and got a rebuilt unit the flange bolt pattern was good and the length are all the same however when i went to install the axle nut it was a smaller nut not what i had this axle also fit the eldorado until 76 and it is a metric size any suggestions? they already have my core so it is gone