Mawk Industries www.mawkindustries.com makes an excellent conversion harness. 12 wires, all Cummins spec. 12 colors and every wire is marked every 6 inches. I'm not doing a CAC. I got 3 spacers made for the intake side to bolt my after-cooler on.
Ed Mawk will go over all the specs and options with you, before making the harness. Mine was $875 plus $20 ground shipping.
I will have to do some re-routing on coolant tubes. I figure on having a muffler shop custom bend some tubing, to do this.
Otherwise, it's a bolt up. Like pulling a 283 out of a 57 Chevy and dropping a 350 in. Bolts right in, just got to do a bit of adapting.
As to the gauges, they are no problem. I'll be running most of mine the same as I do them on my Big Cam. What gauges do you want to run? I changed over from mechanical to electric. Except for the pyrometer, mine are all JJ for a Pete, back lit red. Oil pressure is a sensor in the oil galley running along the block on the driver's side. Oil temp is a sensor in the oil pan. Water temp is a sensor in the thermostat housing. Tach will be changed to the lead from the ECM, instead of off the flywheel. I already have an electric speedo, driven by a tone ring on the output of the transmission.
If you have a mechanical speedo and want to change to an electric, so you can hook up the cruise control, it's not hard to do. There are two options, available. Either replace the speedometer drive gear, inside the tailshaft of the transmission, with a tone ring, or replace the speedometer driven gear and cable with a signal generator and a pair of wires.
It's all pretty simple.