A few drops of oil on the shaft and it all slid together beautifully. There were two circle clips in the rebuild kit and I'm not entirely sure what they're for. One could be a replacement for the expansion ring at the bottom of the core, to prevent the brass journal bearing from falling out the bottom. Since there are two replacement journal bearings, it's probably a new clip for each. I just left the original clip in place since it seemed fine. It is unlikely to fail and would be really hard to remove anyway since it's a coil-style and not a circle-clip with ears for a tool.
The shaft spins nicely and nothing seems to be interfering, so I think things are good to go to the next step: designing and fabricating the combustor. Before I can start that, I need to finish my thermo calculations and come up with a design spec. There are some online tools to help locate the air holes for optimal flow of shield air and combustion air. However, some experimentation will be required before I'm confident to attach the combustor to the turbo.
As you can see, I've rotated the compressor outlet so it's pointing the same way as the turbine inlet. The combustor will mount to the flange I welded to the turbine inlet, and a U-shaped hose will connect the combustor inlet to the compressor. It's looking pretty industrial already and I need to start thinking about how to make this look steampunk with appropriate details for the overall assembly. Lots of brass and stained oak, I think.
Update (April 4, 2014): Work and the need for a MIG welder have delayed my progress. But I promise: more to come!