KMiata offers a swap kit to to install any K20 or K24 engine into a 1990-2005 Mazda Miata. The full kit costs $3,750 and comes with engine/trans adapter plate, flywheel, subframe, engine mounts, baffled oil pan, Type-S oil pump adapter, wiring conversion harness, and install guide. Of course each item is for sale separate so you can opt for using your own parts where you want. KMiata estimates the entire swap will cost $8,000-$9,000 and deliver around 220-230 horsepower to the rear wheels. If you have more questions their FAQ goes over a lot of great tips.
This video shows test car with a K24A2 going around Gingerman Raceway. The engine was producing 220 whp.
Update 7/14/2015 – Matt Farah tests a KMiata at Gingerman Raceway