This is a full ROM, not an incremental update, so it will wipe your /system partition when installing. If you're coming from a non-stock ROM you'll want to wipe data/cache, but if you're coming from a previous stock ROM you should be okay. This is tested in CWM (it's what I have onhand right now) but TWRP should also work.
Changes between this and a completely stock 6.3 ROM are:
REMOVED FROM ROM
- The new /system/bin/check_rooted binary
- Stock recovery image
- Stock bootloader image
- That goofy userdata-backup.zip
ADDED TO THE ROM
- Removed the entry from init.omap4430.rc that ran check_rooted at boot.
- Set ro.secure=0 so adbd runs as root (insecure boot version only)
- updater-script doesn't attempt to install recovery, bootloader, or userdata-backup.zip file since they are not in the ROM.
- updater-script won't check your /system partition's size before installing. This means it will install on a /system partition that's been resized, but I have not tested this. My assumption is that if you resized /system you'll know how to handle any errors that you may encounter.
I'm providing secure and insecure boot images, as with my past versions. For those unfamiliar, insecure means adbd runs as root on your Fire so you get a root shell when you use adb to connect (i.e. you get # by default). Secure gives you a user shell (the $) by default, but you can still use 'su' to elevate to root.
Stock rooted 6.3, secure boot image (md5: 37f51cd2dfaf58baffac09135236de36)
Stock rooted 6.3, insecure boot image (md5: e551a507ebc64fabe09f7d5387348585)