Odd question about modem

[josephdbrewer]

OK so I have the xt1050 variant, bootloader unlocked. LTE isn't fully supported on the GSM side of the phone and no CDMA carriers in my area will activate the phone, the only one that would doesn't exist anymore. I was wondering if I could flash the modem from another variant, could I use LTE on GSM? Or will it mess everything up? If I can do so, which variant do I need to take the NON-HLOS.bin from?

Edit: 1. Sorry, wrong section, can't blame me, blame the app [emoji23].
2. My original os was Android 4.4.2. Mine never got the 5.1 update.