Initially I was using the 4.2.2 version from this link:
It's good for the 6506 and it has no Telcel garbage! Then I upgraded to 4.3 following the procedure and files of this thread: http://forum.xda-developers.com/show....php?t=2567266
Of course you need both root and XZDualboot Recovery to upgrade this way.
All of this is if you want to have 4.3 rooted, if you just want 4.3 on Telcel you can easily flash the latest ftf from the development thread for the 6506. You would have a factory default phone afterwards of course, with no possible way to root it.
Because I've just bought my phone, and I don't wanna void the warranty, though I don't know if unlocking the bootloader voids the warranty here in Mexico