While Samsung may not always update every device with the urgency that we as users all crave, one thing they definitely got right was releasing the same device for multiple carriers with only minimal changes. This makes it very easy for developers and users from different carriers to work together to fix problems, develop ROMs, and have other sorts of fun. For instance, there is now a guide that walks users through the process of porting any ROM from a US variant of the Galaxy S III to any other US variant.
XDA Recognized Developer PureMotive released the tutorial, and it helps end users port both TouchWiz and AOSP-derived ROMs from one variant to the next. As the devices have strikingly similar hardware, porting ROMs requires only a few changes. As PureMotive outlines for TouchWiz ROMs:
In the ROM you want to port – delete /system/etc/apns-conf.xml
Replace the apns-conf.xml you just deleted with the one from the ROM for your carrier
Open up /system/build.prop in Notepad++
Locate every instance of d2att, d2tmo, or d2spr and replace it with d2vzw (Use CTRL+F if you have to)
Save the build.prop after all changes are made
That’s essentially all that it takes to make a ROM compatible with your device. These instructions were written specifically for porting to the Verizon variant of the Galaxy S III, but it can be used on other devices with very minor changes. Porting an AOSP-based ROM requires a little more work, but the idea is pretty much the same. Just make sure that the source ROM is from another US variant, and not from the International SGS3!