One way to calculate value is to start with the cost of a working
vehicle and subtract the cost it will take to get to that condition. I
recently bought an '80 Westy for $2750, I've put $1000 into it already
just to get it legal and drivable and I expect to put another $1000 to
get it in more or less ok condition.  So you might say a running, legal
Westy in decent condition would be worth about $5000.  Subtract the cost
of the engine, labor included, and whatever else you might have to do to
get it going and you have a fair price.  Don't forget to evaluate the
upholstery, paint, trim items, hubcaps, accessories and so forth...those
items can eat up a bunch of time and money in a hurry.
  On the surface, not to presume to be the authority on this...I'd say
$1500 as a reasonable guess.

John Jensen, Mudbug Pottery
mudbug@toadhouse.com , http://www.toadhouse.com