the turbo from an s14 will cause headaches on the FRS manifold. the reason for this is that it uses a five bolt wastegate elbow similar to the standard ERST design so cannot be rotated. as a result the wastegate housing will point at the engine. I'd just go for a good secondhand turbo from the focus rs. that way it fits, should have plenty of power there, and fabrication of the down pipe should be a piece of cake.
HTH

regards

tom