Ernie
Hi I'm Doug from Iowa as well and I organize the Rally for the MidWest Truck Campers. I would like to invite you to this summers rally. I've had many potential TC'ers come to rallies in the past and get a load of info from TC'ers. We all love to help and share info. Check us out.
Here is a link:
https://midwesttruckcampers.wordpress.com/2015-midwest-truck-camper-rally/Now your Truck. Yes your figures seem correct to me.
You say you see many trucks with bigger than necessary TC's on them. Well they have modified their truck which you said you don't wish to do.
This Modification does NOT increase Payload, it just HELPS support it and makes the truck EASIER & SAFER to handle the load of the TC, and its contents. It helps control sway and or roll of the vehicle which with out these products in my opinion will not make it feel very safe to drive for the truck from the factory is set up for a middle of the road payload. So for a Big overload the suspension needs help.
I'm sorry but in my OPINION and its just that my Opinion you will want these items on your truck. My suggestion and your headed in the right direction. Always ask someone who own's and drives a truck and TC. Another words don't always believe a salesman at a RV dealer.
One thing for stability you'll need a swaybar on your truck. This will improve vehicle roll or sway to left, and right in turns.
two you'll want to look into suspension help. Everyone has their own opinion here and what they like or what works for them. you'll get a lot of info here with different suggestions.
Here is what I have, and I have just done a blog report on it. So their are pictures and my ramblings of installation. I recommend Torqlifts products because I've used them and they seem solid, and yet simple. I'm not fond of airbags for I run into a lot of people who usually end up with a leak. Plus I would think if you get any air in a line that it would freeze in the wintertime and something wouldn't work correctly.
link to my suspension installation:
https://midwesttruckcampers.wordpress.com/torklift-international-ambassador-program/stableloads/Yes your going over your recommended weight rating but most all do. Remember lawyers set those weight ratings. if you go over 1500 lbs. your not going to break anything but it you go ridiculously like 5,000 I would start to question things. I was 1200 lbs. over my weight limit.
I asked my ford service tech about weight on my front axle because I was considering putting a motorcycle on the front. He said don't worry about going 1000 lbs. over the front axle rating. Now thats a Ford Super Duty. I wont vouch for other brands.
Good Luck and have fun with the experience. Let me know if i can help. I'm on the Western half of Iowa. How about you?
Doug