that electrical connector is probably your speed sensor / abs (if you have abs option) which runs your speedo . some of the broncos had that sensor in there transfer case up in the top passenger side . with out seein not sure . now on the ujoint it might be the same one or you might have to do what i did with my 69 mustang . when i put the 9" under it the rear end came from a pickup and i had to use the joint that came on my driveshaft for the 8" rear and the end caps of the joint for the 9" (for the truck that it came out off) and make a ujoint out of the two . i guess i might have been lucky on that one cause the shaft part of the joint was same dia. just the over all size of the bearing cap OD was the differance. you might get a magnetic speed sensor set up to run your speedo if the rear is actually your speed sensor.
hope this helps ya good luck
