that is my old car. i sold it to nate, who sold it to lee, who is apparantly selling it to SVT guy. the car is relatively mint when its kept clean. its a nice platform to start from. its the lightest model available. i would recommend against trying to put the S5 NA into the S4 shell... all the wiring and hassle youd have to go thru isnt worth it. like previously mentioned, an S5 4port turbo motor is definitly worth the hassle... but considering you only get 14 more horsepower from going from S4 NA to S5 NA... the time, effort and money you have to invest is NOT worth it. the stock S4 motor is 146BHP, the S5 motor is 160BHP. i would say, GET the shell... leave the motor... then pick up an S4 T2 swap from www.jappperformance.com if they still sell them. and do the S4 T2 motor, tranny, driveshaft, rear end, axles and 5-lug swap with the brakes... dont worry about getting the T2 suspension and sway bars, because the aftermarket stuff will handle better and be worth the time it takes to put it in.

Oh and the pic that Rotary7 posted up as teh 20k mile motor is not the S5. thats the S4 motor that came out of the car. the S5 uses a different solenoid rack with 6 solenoids. the vaccum spider has more lines on it, and i beleive the oil fill neck has 2 nipples on it, not just one. also, those orange vaccum lines are lines i stole off the GReddy profec setup that was on my Then-GF's DSM since i shortened the setup. IIRC, the solenoid w/ the blue sticker is for the EGR... the S5 has no EGR in the same sense of the S4.

if you dont mind me asking, what are you looking to spend to pick up this project car? i only ask because i have an S5 with an S5 motor for sale...

EDIT: i just had the BEST idea EVAR... ive got a Ford V8 engine and tranny mount kit for an RX7. its an engine mount adaptor that bolts in for a small block ford, deletes power steering, and then a trans mission mount for an AOD, and i have the custom driveshaft for the Tranny. right now, i have EVERY thing you need to put the 5.0/AOD in your car. its a $1200 setup as it sits. if youre interested in making the RX7 beat the SVT, here you go... easier than wiring up an S5 motor.