There's a cable that plugs into the sensor, it's probably tucked up somewhere, it's too dark to dive under my '90 right now to get an idea where to look...
A mountaineer axle will be fine, same as an explorer shy of some trim stuff on the body and interior... since you're lowered going to the explorer brake line setup should be fine, another thing to do is grab two passenger side soft lines at the junkyard and cut and crimp nuts on the middle of the hard line so you can use the stock ranger center drop hose...
Your driveline might be good but might be long, on some lower applications I've heard of them bottoming out but yours is probably already modified to fit with the C4...