Difference in stock stereo vs non-stereo

[Pender1]

Was the difference just the wiring, or was there a difference in the head units? My truck came with the single center speaker, can I run some wires and add the two side dash speakers or is there something stopping me from doing that?

 

[Old77]

When it comes to stereos you can do whatever your mind can dream up.

 

[Pender1]

When it comes to stereos you can do whatever your mind can dream up.

I'm good at wiring power and speakers, but for whatever reason head units have always been black magic to me.