Racingher, Thanks for the comments.
You can take your Truck & 5'r to any truck stop w/ scales. (Such as I-74, Exit 143 1409 South County Rd. 850 East Greensburg, IN 47240)
*Fully loaded, ready for the road, weigh the whole package then your truck solo.
One point I would like to make is the use of air bags from a warranty stand point. If you overload your truck (GVWR) and something fails, the dealer/Ford will be hard pressed to buy the notion "well I had air bags on it".
The GVWR on a SRW 250 4x2 158"WB is 10,000 lbs w/ max payload at 3750 lbs. A SRW 350 4x2 158"WB is 11,500 lbs w/ max payload at 3990 lbs.
That's 240 lbs. more for pass., fuel, etc. keep in mind that you have to look at the payload cap. when towing a 5'r
Another way to look at it is; say your 5'r ways 13,000 ready for the road. Then figure your king pin is 20%, that's 2600 lbs. Now Add the weight of pass., dogs?, fuel, 5th wheel hitch, tool box, fire wood, beer, etc. Next thing you know your right at or over the GVWR.
Not that your trucks going to fall apart if its over loaded, just that the extra wear and tear might not be covered.
Happy Trucking/Camping!