Thanks to the many responses I recieved I was able to approach my noisy 
lifter from many angles.  Quick background:  1 lifter had always tapped 
(or loudly "clacked") occasionally on startup but always went away after 
warmup.  Recently (150k) it had become unpredictable and much more 
frequent, sometimes reappearing after hard freeway driving.  I am very 
happy to say that 1500 miles later the sound is virtually completely 
gone, only occasionally now I will hear a *very* faint tapping for about 
5 seconds after startup.  Heres what I did: first, I added a can of 
"Justice Bros additive, for sticky lifters and valves" (thanks Volks 
Cafe).  Then I *drove* the darn thing:  I went to Big Sur 4 times in 4 
weeks (150 rt ea. time, Phieffer was nice).  Then, I changed the oil (a 
little dirtier since the additive) and installed an OE Mann filter.  I 
used my usual Castrol 20w50 GTX.  "Kermit" purrs now, even quieter then 
when I purchased him!  In my opinion the most important thing I did was:
1) Used Mann filter.  The old one was a South African brand, GNB or some 
3 letter initial.  
2) Used additive to clean out crud accumulated by not letting the van 
warm-up properly and (recently) less road trips.
3) Drove it!  I agree with those who said that short cold running trips 
gunk up the engine.  I cannot afford another car for commuting, so the 
solution is to take the van on the road more often.  I think I was 
forgeting how easy it is to just jump into the Westy and head-out.

The noise may never completely go away, but I can certainly 
live with it as it stands.  Also, I went to Fred's Garage in Redwood 
City, and they positively assured me that it is only the lifter losing 
pressure, that replacement is unnecessary and that it will *not* cause 
any damage or reduce performance.  
Thanks for all the help!

Charles
'83.5 Westy