Quite a few solutions. The Real QT exporter should still work. If you are having problems, then I would highly suggest Episode from Flip4Mac. Best Real encoding on any platform IMHO. Squeeze does a pretty good job as well, just not to the exact same level of Episode.
Although I haven't tried it on the Mac Pro, the exporter was only approved for sys 10.3.x. On my previous edit system k(dual G$) I had issues using it with system 10.4.x and FCP 5.1.x. On the Flip4Mac site, Real was not listed as an output option for Episode. And on the Sorenson site, there is a note that Real encoding does not work on Intel Macs. If someone is acutally using any of these options, encoding Real Media on an Mac Pro, I'd like to hear from them.
Right, I didn't pay attention to the fact that you are using a Mac Pro. Real encoding is not possible on Intel Macs yet because Real and the Helix community have yet to port the libraries over to Intel. So for Real encoding and the Mac, you will need to use a PowerPC mac. If that option is still available to you, then I would suggest Episode as the encoding suite. While you are correct in that it appears that there is no mention of Real on the Episode site, if you download the data sheet there is info there. And from my tests over the years, Episode (and Compression Master before it) has always come out on top to be the best Real encoder.