Yo.  I hopped in my friends syncro and the clutch pedal is like butter.
Mine is considerably stiffer and crunchified.  I've checked the archives
about this issue, but now it's time to ask the masters...

The patient is an '89 Westfalia, 205k, with a rebuilt 5spd installed about
75k ago with a HD Luk clutch kit.

I'm sure the problem isn't hydraulic (swapped out master and slave a while
ago to no avail).

So is there a simple and obvious way to determine whether it's the pedal
assembly, or the release rod in the clutch housing?  Perhaps that it comes
and goes may be a clue?  FWIW, there isn't a lot of play side to side in the
clutch pedal, feels like the brake.  When replacing the slave, I yanked
around on the release rod and it had some slap in it, but didn't feel too
loose.

Statistically speaking, what's more likely to be the issue?  Do I rip out
the dash, or drop the transaxle (again)?

Grazzi,
-R