that looks like Wagz car from twinturbo.net. i asked him the same question, and i think he said it was a custom job. you can also get widebody kits from Z1 Motorsport in the US, and Strosek (in germany i think).
That body kit looks very similar to a range of wide body kits you can get from a mob in England: http://www.zcentre.co.uk/index.shtml
Re: That body kit looks very similar to a range of wide body kits you can get Yeah close, but this one has a one-peice rear and better moulding into the side skirts. Oh well I'll keep on dreaming then....
Like lysergic and fleet said.... The widebody is custom. Very well known car on ttnet. You can find all the details and more on there with steo by step pics of the build. Basically if you want anything near as nice then this is the only way about it.