some 1/8 scale monster truck bodies may fit....think HPI Savage.
Or, you can buy a redcat rampage 1/5 body for it. I had an exceed 1/8 crawler which I built a custom frame for and used the rampage body. for the exceed, I had to lengthen the wheelbase some....but I think the rockslide may be longer than the exceed. I know the rockslide's tires are a bit taller than the exceed's....so the body would have to mount a bit higher or the wheel wells trimmed more. But I am sure it could be done. Here was my creation: