You can install ROMs for the d802. Just be sure to immediately flash a kernel for the d803 before booting.
ROMs for the d800 or d801 may also work, but I've only tried d802 ROMs myself (Omni and Slim so far).
There are kernels and ROMs for our phone in the generic Android Dev and Original Android Dev sub-forums here.
Typos courtesy of my LG G2 (D803) running Slimkat.