If you are really interested in something different I would say twin charging the Sr would be the best bet. Space is still a huge factor and I have only seen this done on RHD silvias.

Basically you are supercharging the turbo. Depending on the SC and turbo on how it will be set up. For a centrifugal blower would make power up top you would add a smaller turbo for down low. Or if you were to use a Roots type blower...etc

i will track down pics in a sec.

 

You can find the debate on fresh alloy