Any time you do anything with gears you will have to reset the backlash (and often times you have to set the pinion depth too). Each differential is different, its why shims have to be used to adjust the backlash and pinion depth for each individual differential.
Ring and pinions are also matched sets, mixing them will cause them to wear very quickly and be weaker. Even thought the gear strength probably isn't much of a concern with a FF14 bolt the metal running through the bearings is.
If you want to just swap carriers in a 14 bolt its not too hard and there is a tech article on pirate that will tell you more than you need to know. Always, always, always clean the bolts (and always use brand new ones) and always use loctite, otherwise you'll be doing it all again in short order.