Help with wheels and tires.

I will fill up with diesel and weight my rear and see where it is at empty. Then I'll add 4500 to it to be safe. The 4500 would include gear and water and 90% of the time we have water hook ups at the camp site so I won't have any water on board. I will take water only on my hunting trips and some rare dry camping. I really like the best of both worlds for tires. I have 2 friends with same camper, one is a 2003 da,the othe a 2012 Denali 2500 diesel. Both run stock wheels and only one has upgrade to 285's. One pulls a 20' north river boat and the other a 12' enclosed trailer. I guess I'm paranoid at having a blow out. I hunt and I'm off the highway a fair amount so if I could make a 16-18" wheel and tire combo work with out moding the front suspension and still be within tire limits I'm all for it!! I have increased my budget to $2500 but less would be better if poss. I will also have a 20' jet boat within the next 1-1.5 years so it want to be set up for when that time comes also. I need to check and make sure the camper I put money down on is the "s" 811