WHY! would you want to put an motorbike engine in a car?! a lad i know has a front engined R1 powered mini, and its not amazingly quick and the noise is just stupid.
take a look on 16vminiclub.co.uk vtec, 2.0 vaux engines, and the small block vaux engines, (im currently doing a 1.8 16v) are the favorite conversions. subframes can be bought off the shelf too.
try allspeed engineering. pricey, but all the R&D is done and they bolt straight in.