I've become the technical adviser for my non-technical neighbor, who has a 2000 Sierra 2500 non-HD. The truck pretty much lives with a landscaping trailer on it, or a bass boat after working hours (I'm out on that boat a few times a week, so I like to help him out). So the receiver is worn out. The receiver tube is pretty sloppy and the crosspin hole is a nice oval. He wants to fix it, and I suggested that the best way to fix it is to spend $150 and just get a new Curt/DrawTite/Reese hitch. He thinks that's a good deal, so that's easy. Anyway, I looked at the practically-unreadable sticker on the old hitch (OEM probably?), and the only thing I can see is "5000", which is about right for a Class 3 hitch. It's got pretty beefy frame brackets, so it's probably OEM and is underrated for the actual capacity. Class 3 hitches for that truck are mostly rated for 6000 pounds. I like a bit of extra overkill, so I'm thinking a Class 4 might be a relatively cheap upgrade (extra $40) and bump up to 10k-12k pound rating. Same receiver size. Is there any reason that a Class 4 wouldn't be a drop-in replacement for the existing hitch if they mount the same way, etc....?