No, probably not

I really depends on the model.
Base model wiring harness will not have any "optional wiring"
If your model had a 4 speaker Stereo "option" then wires will be there
You would need to find a 2003 Ranger brochure online and see what model had what options, they changed yearly

Try this site: https://www.cars.com/research/ford-ranger-2003/trims/
Looks to be 16 trim levels, each will have "optional" equipment adds for that one trim level

Each year usually had Fleet Models as well, very basic models sold to larger companies in bulk, so no option wiring at all

 

Thank you very much. I'll visit that site. The truck is a base model however it has speaker grilles where rear speakers would be.