ok ive searched and read multiple threads about swapping interiors and its pretty much been determined that cosmetic pieces swap out and be fine
however
im purchasing a barebones shell and i mean barebones like no doors etc and will have to swap in the entire interior (or at least what i deem necesary to drive the car) and was wondering if there was any differences in some of the underlying components AND how they mount such as power window motors, sunroof motor, harnesses to run power etc to different locations
ultimately it is an s5 shell and i assume there are some of the interior harnesses left and i have an s4 that i can strip out anything necesary from so im just wondering what would work and what wouldnt

any feedback would be appreciated

 

The FSM has all this information, and if you have a bare bones shell, then yes everything is interchangable.

 

What about the belt system?

 

It's still interchangable in the fact that you can install S4 belts in a S5 chassis. Not sure about the other way around, but in his case it will work fine.