Which engine depends on what your plans are. If you do a K20/K24 hybrid, then it really doesn't matter which engine you pick, since you will be swapping the head anyway (if you're lucky, your head is salvageable, so you already have half the swap done). The TSX engine makes it easier, because it already has the proper engine management. If you get the accesorires that come with the engine, most everything should bolt up. You might need new engine mounts, and a specialized header (to clear the rest of the engine bay). It would be wise to ask HASport exactly what you need to move the engine.
Here's how to build the engine:
Short Block with K20A2 VTEC Cylinder Head - Tech - Sport Compact Car Magazine