Talking about alternators and brushes, my experience with Detroit iron
has been that about 80% of the 'alternator failures' were nothing more
than worn brushes.  This was confirmed for me by an auto electric
rebuild shop employee many years ago.  Am I safe in assuming the same
thing with the alternator in my '90 Westy?  If so, then I'll and a
brush/regulator assembly to the 'long trip' spares kit.