you'll get more answer if you post in Toyota Section. there are sifoos that rarely post outside toyota section.
anyway. 3sgte would be abit too big and heavy and will ruin the balance of the car. its not really a good choice unless you are after drag racing. AE111 is an FF layout car, thus having a heavy front end might make your car understeer all the time when you turn into the corner.
turbocharge your 4afe is another choice of course, there's people who is doing it. go for NA or Turbo is up to you. If you want turbo, most people in the toyota section probably suggest you get a 4agze and turbocharged it (sell the SC). OR, get a 6 speed blacktop halfcut from jdm ae111 and swap everything over.
i'm not very sure, but i heard that putting 3sgte inside AE chasis not only upset the balance, but also abit too tight. you basically can't do anything to it once the engine is in cuz there's just not enough space. imagine something gone wrong with the engine and you have to take the engine out to fix it.
just my 2 cent. cheers.