I know this has been done before, I'm just wondering exactly what needs to be done to make it fit.

 

yeah i took it off my s5 and just stuck them in my s4

 

You'll need to have the S5 air vents since the S4 ones won't fit, but usually when you pick up an S5 radio surround it will still have the vents in it. If you want everything to match in texture, you'll also want the S5 shifter bezel since it has the same rubberized surface vs. the S4 hard plastic.

I guess the only other issue you might have is that the vertical spacers for the radio are separate pieces in the S4 making them easy to notch or remove to accommodate aftermarket stuff. On the S5 surround, they're integrated into the entire molding, but again this is no big deal.