I'd say you need to measure to see if you have enough length to go the extra two inches. They might have already replaced the stock when they went to the 12". From your pictures I would guess they already did the wire harness extensions and you should be OK there, the clutch cable looks like it probably has enough play, the brake line looks plenty long enough, but those throttle cables I would guess need replaced with longer ones.

 

On my 2016 FXDB I just changed the throttle cables. I was able to reroute the clutch.

I had 14" Burly Narrow apes on there at one time.

I still have the extended clutch and brake line in a box somewhere. Burly sells a kit for the cables.