Update: someone on another forum gave me a tip to slightly jack the front of the engine so that the flywheel pointed a little downward, which would give enough space for the hump on the bellhousing to clear. Worked like a charm (well, it did once I remembered that the transmission needed to be oriented on an angle to match the engine!)

Now, "the rest of the story": I had the KM145 transmission rebuilt this summer, and a few weeks ago the transmission locked up at a stop. I pulled the transmission, took it back to the shop, and invoked the warranty. Now, when I reinstalled the transmission the first time, the input shaft was pristine ÔÇö not a mark on it. When I pulled it out this time, though, there was a groove warn in the input shaft where the pilot bearing rides. The transmission place said that the pilot bearing had bound up the input shaft, and if the tranny was in 4th gear and the clutch pushed without downshifting, the 4th gear wouldn't disengage. Sounds reasonable, especially since I saw the damage with my own eyes before they got their hands on it.

This time, instead of trusting the cheap $4 pilot bearing that came with the Sachs clutch kit (supposedly a quality part), I ordered up a made-in-Japan Nachi (which I'm told is OEM) bearing and installed that before reinstalling the tranny.

I hope this is the last time I have to pull that thing for a long, long time!