would a 1999 ford explorer stock stereo/head unit fit in a 1999 ford f150 xlt?

 

It might fit. Measure the size of the unit in the F150 and the Explorer to see if they are the same size. Even if the unit itself is smaller, they sell adapter kits to fit the vehicle. The only issue might be the wiring harness from the F150 might not be the same as the Explorer, so you may have to figure out how to get the wiring to work.