Im going to sub in for ideas here.
I have installed 3-4 05 up radios when doing 6.0 to 7.3 swaps. I had the pigtail from the 05 up trucks and used an aftermarket harness to splice it together and plug into factory 99-04 harness.
Almost all the wires were the same color. Main change was another switched 12+ and an extra ground. I hooked them to together on the aftermarket harness, and "boom" plugs in and works fine on the first 3 or 4 trucks.
Only 2 extra wires on the 05 to do with the speed vol control. We have done 2 of these this year, and I can not for the life of me get the 05 radios to have sound!!???
Raido powers on, all controls seem to work fine, but nada for sound. I even have voltage coming out of the radio and at the speakers, but ZELCH for sound? So for the last few weeks all I have been asking myself is WTF am I missing here?