I honestly didn't think such a transmission existed, but now I understand RC4WD did release a 1:1 version for their worm drive rock crawler - because all the reduction is in the axle.
http://www.rc4wdforum.com/showthread...o-Transmission
Can't really offer up any advice. I wouldn't have known such a transmission existed either. Perhaps you can just buy the gears from a reduction R2 and swap them in your trans case. I find it really hard to believe that RC4WD would have designed the case to be different. From a money making standpoint, it would make sense for the difference to be in the gears and not in the case. That way both transmissions could share the case. I think RC4WD sells replacement gears. I'd ask them.
Edit - it does look like the cases are different, so my suggestion might be of no help!