Shedding Weight on an M22


I have been looking for a refurbishing project. My preference was getting an Edge M21, but they are hard to find and the ones that are for sale are double the price they should be. I have found an M22 for sale that had a water heater leak that flooded the floor up to the baseboard. The floor needs replacing for sure. The problem is my tow vehicle is a Toyota FJ Cruiser (5000 lbs tow rating). I do not want to tow more than 4000 lbs. The M22 dry weight is about 3900. Any ideas on how I could lighten this unit up, say drop about 400 lbs? I am thinking that the wood cabinets could be replaced with aluminum ones, but I just don't know what the weight savings will be. The plywood subfloor could be replaced with an aluminum one, but again, not sure what the weight savings would be. Any ideas would be helpful. Thanks.