Component compatibility, S4-S5

[RETed]

In short, most of the electrical components are not swappable.
Most of the electrical plugs have changed between the series, so it's not a drop-in swap.

With that said, why do you insist on the stock stereo components?
Unless you just want to resto or keep it nostalgic, aftermarket stereos are just superior in every way.
With the advent of MP3's, going with a modern head unit is a no brainer.
Aftermarket head units are CHEAP now - most are under $200 with great sound.
No need to deal with the stock wiring except to get power, +12VDC switch, and ground.
Run all new speaker wires, as your stereo system will thank you for it.


-Ted