Really depends on what you want from the car. 4age is fun , but not earth shattering in terms of power. You can turbo one , but the costs skyrocket pretty quickly.
SR20 needs custom mounts and wiring, which keconversions can provide. He can also provide mounts to suit the ke70 xmember too. You'll also need a hydraulic peddle box no matter which way you go.
Kaizen garage would be where i'd start to get the conversion done. and speak to Anthony.
My advice, buy a second car use that as a daily and then convert your ke70.