Key word though is build. If you are looking to build then hobozcar has the best idea. But either way, it won't be cheap.

GSR B18C Swap --> $2,700 - $4,000 depending on type of swap
SiR B16A Swap --> $2,000 - $2,700 depending on swap

Prices will vary depending on what you want, complete stock or long block only. LSD Tranny or just hydraulic, ecu, wiring harness, etc...These are all things you will need to think about.