This is a very good Chevy GMC VIN decoder:
VIN Decoder - Chevrolet Forum - Chevy Enthusiasts Forums
Couple that with this GM RPO (regular production options) lookup and decoder:
GM RPO Lookup
and you'll get a lot of info about the Chevy / GMC vehicle that you are looking up
a bit more on the RPO lookup here: http://www.classbforum.com/forums/f5...oder-1748.html
I'd like to find a GCWR lookup site to help answer towing questions when they arise on the forum.
The original 1997 GMC brochure for my van is the only source I've found for comprehensive GCW ratings for this van. The VIN decoder site above is good but it shows two GCWR's in the results for my van. You's have to already know that is because of the two options for the rear axle ratio for this particular van (diesel engine). You can find the axle ratio when you lookup your vans RPO codes.