Found an Alpine thats in a 07 non bose Z and tryin to figure it out if its wiring harness will work on my 03 non bose

 

I would guess that they would be swappable (assuming they are both non bose).

It would be fairly easy to check - look up a Metra wiring harness number for an '07 non bose Z and the Metra wiring harness for an '03 non bose G35 coupe. If the numbers match it is likely the harness will plug in. If they don't match the harnesses are only around $20.

This also assumes that who ever installed the Alpine in the Z used a harness and didn't cut the wiring up!