This is a thread for d803 owners to discuss how we're going to get LTE supported in KitKat.
Right now, if you flash the popular KK_Baseband floating around, you'll get "4G" after either deleting lteconfigs.apk, or tweaking your build.prop (depending on your ROM). So don't expect "4G" right off the bat, however, even after doing all necessary tweaks, you'll likely find what I found:
"4G" is not 4G, it's HSPA+ in desguise. You can tell by running speed tests (and also noting that the Network always reverts to GSM/WCDMA), they are all within HSPA+ speeds. Reverting back to JB, and running the same speed tests in the same areas results in MUCH faster speeds as it's true LTE. Meaning: 4G does not equal LTE.
Now, I know what you're thinking, "this guys a newb and didn't do the tweaks needed". No, that's not the case, I did all the tweaks, I tried this on CloudyFlex, CloudyStock and even the Rogers KK ROM floating around, all were stuck on GSM/WCDMA with "4G", which is really HSPA+.
So this being said, there appears to be no way to run a custom stock ROM, with LTE, I hope I'm wrong.