[Average Joe]

IMO there is nothing wrong with cutting up to 1 full coil off a stock spring. Im not sure I would cut a 3" drop spring though. Like others have said if you do cut be conservative. In my experience 1/2 coil only got me 3/4" drop on a newish stock half ton spring. When I cut the other half off after driving for two months I gained 2 more inches of drop for a total of almost 3 inches. The ride was only slightly firmer afterwords. You may want to consult a trusted alignment shop to be sure your camber can be corrected if you do lower more. Have you considered a firmer spring in the rear specifically for a Burb or panel? Supporting vendor GMC Pauls sells rear drop coils in 3 or 4 inch drops that compensate for the additional weight. Another option would be a 2 inch lowering block in the rear with a stock coil. You can build your own or buy them from Borris in the suspension market place. HE goes by way2low2.