if you want to turbo it do you realise there was a limited edition turbo corolla made in australia? it may be possible ot find a turbo manifold & modified ecu around that will bolt to the 7af (i know someone who priced a turbo ecu from toyota late last year ans dell over laughing - it was over $10k!!)
otherwise go the 7age - then you can use ahks type exhaust manifold.
you will need to change the rods & pistons - this can get expensive.