motherboard switch I phone 4

I have two iphone 4s, exact same model (A1349) one that I have working with Sprint and the other just a spare (turned off) from Verizon- here's the deal, I would like to switch the motherboards in order to give the phone that I use more memory for storage- 8gb to 32gb. My question is about the carriers though. Does it matter if the carriers are different between the two phones, given that the rest of the phone (aside from storage space) is exactly the same? What about a variance in software/firmware versions? ie- If I do just switch the boards, I have no problem resetting the phone completely, but would this somehow interrupt my account with Sprint? I'd keep the SIM with the same case, I'm really just aiming to upgrade the storage.

THANK YOU!!!

P.S.- I've successfully switched other parts in other iphones, phones, mp3s, and computers, I have all the appropriate tools and know what to look for in a match (in hardware). I've never come across this issue with different carriers before, I've always just done same for same replacements. Money is no question, I already have the parts. I don't care about warranty either. And I don't want to just use the other phone, they're different colors as well.