This seller on e-bay has been listing NOS (really, I got one its MINTY) 'late' style open cab canvas tops for $50. These are the nicer tops with the metal reinforced door openings.
$50!!!!!
A new made top from one of the canvas dealers is $300+
http://cgi.ebay.com/GMC-Truck-CCKW-Top- ... 3a62f93827
When I got mine he had 10, he's now down to 8. Where else are you going to find an NOS top for $50?
Best deal going for a CCKW part.