Don,
It's pretty easy to get 1100 lbs of junk onboard, if not on day one, shortly thereafter. You are going to add around 60 lbs of propane right off the bat and the water tank won't be completely empty either. Water is 8.4 lbs/gallon and adds up quickly. Then add canned goods, beverages, etc.
And what about tools? I'll bet you carry a bunch and maybe some spare parts too. You can get a couple hundred lbs in a hurry.
Everybody says they will never carry much stuff and just about everybody soon makes a liar of themselves, adding this and that until the weight has grown considerably. But only you can decide. If you take the gamble, please weigh the rig when loaded for the road. Do it soon after you get it and do it again in 3-6 months. Let us know the results, but I'll bet you are shocked at the way weight has grown.
The FB series is a travel trailer, so you won't have a lot of money invested in the installation of a fifth wheel hitch. It probably won't cost much extra to move your towing gear to another truck if you decide to upgrade the truck after towing a few times.
almost
By the way, get a good quality weight distributing hitch. Don't skimp on that part. We have heard a lot of good reports on the Equalizer brand lately, but the Reese Dual Cam WD hitch is the tried and true solution.
One more factor: your 4.6L engine is a very small block (small displacement) and they don't have much reserve capacity for heavy loads. If you had even a 5.0L I would be less concerned about performance, but these little engines rely on RPMs to generate horsepower and their low end torque & HP is all but n-existent.