Domestic unlock for Sprint variant

It's been awhile sense ive been on here. While I was here there was a different guy working on the cm12 port and with that he spent a lot of time getting GSM working on the Sprint version. Now it's someone else and its for all variants so its been really difficult to find out what the process is. For most phones you have to do something special before flashing but it didn't seem that way last year when I had the phone. I want to give it to my daughter's mother who is on gsm straight talk. After rooting the device could I simply just flash any custom rom and gsm is instantly available or is there another step I'm missing. Ive searched a bit through the Q&A and general but because all variants share the same section I can't find a direct answer for my Sprint model.

Could someone please direct me in the right direction

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