O2 sensors

[sebby55]

Went to the dealer for O2 sensors they tell me all 4 are the same part#(they didnt give me the part# a**hole's)went on line found some sites have a different part # for before the cat and after the cat.This is the pre-cat#AC delco afs106 -post cat part# ac delco 213-819 are these correct.Thanks for the help.
Also changing the cats Walker or Magnaflow any suggestions?

 

[hoe]

they maybe the same sensor, but the pigtails are different. 1 male 1 female. thus 2 part #s. For a kitty go with magnaflow.

 

[sebby55]

Thanks for help