I see no compelling reason to buy new if you're planning a conversion down the road.
Not much has been changed on these bikes since '87, and ultimately you'll be using very little of the original hardware.
If you want a nice, reliable toy far into the future and don't plan a conversion, new would be the way to go. Otherwise you might consider a good clean '01-up unit for less than half the cost. Same bike, same eqipment.
Just my .02. You'll be ditching $3500 worth in hard parts for 10 cents on the dollar after the conversion if you go new