Well I've been searching and reading about the differences in 13b housings, one of my s5 t2 housing is bad, rotors and side housings are good, can I use s4 n/a housings on the s5 to rebuild the engine? I just want a running engine on the stock level, from what read I need to modify the exhaust ports and the coolant passage for the turbo, what im concerned is the spark plug holes since the leading is on different position I would just need to play with CAS and retart the timing a bit, also the location of the knock sensor bugs me, where or how can I install the sensor since there is no place for it?(S4 is in center iron, S5 front housing) Has anyone done this?

 

Yes, I have done it. Do some more research. S5 front cover. s4 keg with s5 internals. Not hard. But knock sensor isn't that hard to hook up. Just drill and tap.