xr/crf 50 exhausts fit with a little modding i fitted a DOMA race pipe to mine with a extra small bend to it and fitted straight on,others pipes fit and all you have to do is make a bracket and bolt it to where the grab handle bolts on to...........
i done a thread on this ages ago on the crf50 or roost page or the off topic page a long time ago but no one was really intrested,go on GlamisDunes.com :: Information Regarding Glamis and the Algodones Sand Dunes there hundreds of custom built atc 70 on there with loads of links to custom parts,trails bikes even do a 88 big bore kit wit hbig valve head for the atc 70 as i got one but havent got around to fitting it yet....