I have investigated this for my P410 sedan. Things to consider;
[*] Gearbox - do you intend on using the gearbox from the bike? If yes, you need to consider that there is no reverse with a bike gearbox, so options are to do some expensive machining and stuffing around to mate a gearbox up OR most use a starter motor on the tailshaft to achieve the same. Just understand the limitations of a gearbox that wasn't designed to be moving a lot of weight, and a starter motor that probably isn't to well equipped to rotate a big weight limit either.
[*] Where are you located? You may not legally be able to do the conversion in your state, I haven't found much information on this. There are conflicting opinions, some seem to suggest the bike engine once removed from a bike becomes a "engine", therefore with that thinking as long as the vehicle it came from passed emissions technically there should be no issue achieving engineers. Others suggest you simply cannot put a bike engine in a car, again I haven't found anything to back up this opinion.
[*] Assuming you use the bike gearbox, you'll need an adaptor to convert the gearbox spline to a flange that is compatible with a tailshaft. Apparently some buggy places in the USA sell these for certain bike engines.
[*] To mount the engine you'll have to create some sort of frame, doesn't look too difficult, the ones I have seen seem to use round stainless thick solid bar that goes around most of the engine then mounts to the chassis/crossmember via usual methods.
[*] You'll be making your own extractors most likely.
Check out this guys car for some good details, I love this thing
http://www.speedhunters.com/2014/02/a-k ... nja-power/
It isn't a great deal different from doing a normal engine conversion, other than the extra bits mentioned above. Cool things you will get;
- Noise!
- Sequential shifting
Hope that helps.