I have been successful at replacing 2 timing belts ('82 B21 and '83 B23) without removal of the crank pulley.

You can remove the 6 bolts holding the v-belt pullies and take the whole set of pulley haves and spacers off, leaving the timing belt sprocket. remove the tensioner and walk the belt off the cam sprocket. From there you can thread the belt in at the crank sprocket, align the secondary shaft marks with the belt, then walk the belt on the cam shaft sprocket while working in the tensioner at the same time.

Its probably harder and takes a few tries to get the alignments correct unless you have some help to hold the belt taught while you align it on the crank sprocket. I set the positions of the secondary and cam shafts first and then rotate the crank shaft to the right spot and start the belt from there.

Hope that helps someone.
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'82 245 B21F-MPG (LH 1.0) 192k, '83 244 B23F (LH 2.0) 164k