I bought this 1997 GMC sierra and it had a "Sure Pull" hitch/receiver on it. The hitch has a sticker on it that has a couple different weight ratings on it(5,000 and 10,000 pounds). This is my 1st real truck(had SUV's in the past) and I'm not familiar on towing and ratings. So how how much is this hitch/receiver rated at pulling? Is it the 5,000 or 10,000 lb rating? I know the truck is not rated at 10,000 but I think it could handle 7 or 8,000lbs. Also is this a class III receiver? Here is a couple pictures and you can see the receiver on the truck on the bottom picture. Thanks for any info!