As far as I know, the only way to install true unrooted stock roms are either by the RUU or by flashing a zip file in the bootloader. Either way, you will have to get into bootloader. Anything else will be custom roms. You can install a custom stock rom and try uninstalling superuser, but it will reflect custom software in software information. Going about it this way, may apear to be unrooted/purely stock initially, but anyone with general android knowledge will be able to tell that its been fooled with. Especially if they try to perform an OTA software update from AT&T and it won't work because it's been rooted. And then, of course, you can't forget about your phone being s-off.
Samsung Galaxy SIII SGH-I747
AOKP Task650 Build 1.26 | Android v4.2.1
CWM Recovery v6.0.1.2
Samsung Galaxy Note 10.1 GT-N8013
Redemption ROM v3.2 | Android v4.1.2
CWM Recovery v6.0.1.2
|