My 99’ c-cab was orginally a 7.3 but the guy I previously got it from threw a 6.0 in there, a lot of the wiring is rigged! My main concern is the a/c he has a switched 12v running to the compressor and high pressure switch can some help me with a diagram or advice to redo/make a new separate harness what can I do in this situation

Did you find your schematics?

I can send you the 99’s schematics, and a repair there shouldn’t be too difficult.
The 6.0 A/C system had the comp cycling relay under the grounding control of the PCM. I can provide those as well if needed..

thanks for the info!