As you're already swapping the interiors (I assume this means the dash) then swap the dash harness with it... No muss, no fuss. You could have the cleanest possible swap out there if you take your time and compare and swap what's different. There's nothing easier than a COMPLETE swap from an already intact and functioning vehicle. Light at the end of the tunnel. ;)

Otherwise I do believe some of the dash harness wiring will need to be modified (just a few wires, but I can't recall what).