FLM may not offer the wide arm conversion for the rear because you can just use a wide offset wheel. The front already uses a wide offset wheel and can't get an wider that way.

I'm not familiar with the Jato conversion but I can see how that would work. The other way to widen the front is to use the Pede's rear arms up front. I did this once years ago, not much to it but I think you need a new longer camber link in addition to the longer steering link. Jang over at URC has great documentation on the mod and may have been one of the first to do it. Just google Stampede wide arm conversion or see the Jang's here.
http://www.ultimatetraxxas.com/proje...ede/phase2.php
http://www.ultimatetraxxas.com/misc/...pede-wide-mod/

Edit: For the chassis it is pretty easy to lengthen the stock one with some flat aluminum or angles that you can get at a hardware store for under $10. Another easy way to go bigger is switching to a Slash chassis, just cut the sides off if you need to. Pretty sure all you'd need is the chassis, steerin bellcrank and the front skid/chassis brace, you have everything else.