<REQ> GVWR for 91 Silverado

I bought a used 1991 1/2 ton silverado, extendacab, 6.2 diesel, 4 speed automatic. Does not look like it has the trailer package : no transmission cooler (yet) and the rear springs look normal. There is no door sticker that has the GVWR. Does someone have the same truck that can maybe please take a run outside and let me know what it is? I want to do some hauling but don't know how much I can haul without the GVWR to get me started. I tried GM, but their service center said they don't keep the data after 10 years

BTW if anyone is trying to find the maximum load to be carried here is a nice worksheet
/http://www.rvsafety.com/gvwrworksheet.htm

Well, my Dad has a 91 1/2-ton Silveardo regular cab with a 5.7L and 4-spd auto with limited slip .342 axel ratio and its GVWR is 5600 lbs. My truck is a 92 with teh same set up minus limited slip and it has a GVWR of 6100 lbs, and my cousin has a 92 extended cab with same set up as mine and it has a 6400 lb GVWR.

hope that helps.