[RC-Monster Mike]

It has a lot better chance of fitting than the Ofna motor mount. I am about 99% sure it will bolt right onto the GS truggy - the only issue i can see is that the truggy shown here has a large spur gear, which will limit gearing selection(perhaps using a buggy spur gear is an option?). I have never had a GS truggy in my hands to verify whether or not the parts are compatible(or I would have mentioned it in the product listing as you suggested), but if I was a betting man I would say it will fit. It isn't likely that GS reinvented their center diff bulks when they made their buggy into a truggy. :)
If you purchase it and it doesn't work, I will gladly accept it back - as long as it is still saleable as new(if you drill it, scratch it up or otherwise disfigure it, then thisis a different story of course). We have Mod1 hardened pinions as well(we were the 1st to offer these, actually). :)