I'm not sure what the RR 48 or 50 is. I run my TA03FS with the white 0.4 gears and the 29T pinion with a silver can 540 and it's among the fastest cars that I race with (silver can 540 race class.) It fits in without a problem and I have tested to make sure that larger pinions work using 64 pitch. I went as high as 32 since that was the biggest I had, but I can't ever imagine needing to run that low of gear ratio. I easily make the 8 minute runtime with 2400's too, so I could run with a larger pinion if needed. Hopefully that helps!