[rescue] WTB: Good 'antique' computer for education

[Big Endian]

My fiance is looking for an OLD computer to teach herself some 
computer architecture.  I'm thinking something with a card cage.  My 
personal favorite are the VME based sun machines but I'm open to 
ideas.  I need something where she can get replacement parts cheaply 
and (relatively) easily.  Would a VAX be good for this?  What about 
an -11?  How small can I make an -11 or a VAX?  Does anybody have 
anything they would be willing to let go or a place to get this kind 
of stuff?  (I wouldn't mind getting a VME sun... Especially not an 
4/xxx deskside one)
daniel