I have an '82 diesel Westy with 35K miles, always garaged.  I got it from my
in-laws when it had about 30K miles.
A new head gasket was put on at about 29K miles.
I have done the normal oil, coolant, and filters type of maintenance.
What preventative maintenance should I perform??  Someone once suggested to me
to replace the head bolts with different/new head bolts which will not
"stretch".  Anyone know about or recommend this?
I would appreciate your help and experience as I plan on keeping this car a
long time.  It only gets used about 3K miles a year.  I firmly believe that
proper preventative maintenance saves much $$ over the long haul.
BTW.  I put the yellow bottle Prestone in last year and my water is very soft. 
Did I make a mistake? Should I change it immediately?  Is there a procedure for
bleeding the air from the system, I did the bleeding last time at the radiator
bleed screw?
THANKS!!