6.0l cabs

[Bobus]

So I did a cab swap last weekend. I put a '05 cab and front clip on a '03 chassis. So I found that the ABS is a bit different (location and wire plug) so I was gonna just swap in the '05 ABS unit but I found tonight while starting to connect wiring plugs that chassis wiring is different on the 2. My '03 only has 2 plugs while the '05 has 3.. Anyone know what the 3 is on the '05? Also can I just swap over underwood harness from the '03 to the '05 or will it not plug into the firewall or will I need to do dash wiring too? Just trying to find an easy solution to this issue.. Both trucks are 6.0l trucks