Yeah, 4.5 mpgs would be about right pulling that kinda weight. You really need to step up to a CTD when you can afford to...

 

Isn't Ford claiming 11k lbs for a plain-jane F150 these days? They must be made of magical materials.

 

That is a heavy fifth wheel. If you do upgrade, I would highly recommend DRW over SRW in a 1-ton model. You most probably are pushing 2500-2600 lbs for the pin weight which is definitely putting you over your GVWR for the vehicle. A 2500 Cummins will actually have less payload because of the extra weight of the engine. I tow a 32 foot TT that weighs a little under 9000 lbs loaded and I pull it with a HEMI Mega Cab with 4.56s. I pretty much only tow in flats since I live in Louisiana and pretty much only tow in the Southeastern part of the US. I get between 7-9 towing.

 

Specs for a f150 platinum supercrew (loaded to the hilt):

Maximum towing capacity: 11300 lbs.
Maximum payload: 1760 lbs.
Gross weight: 7100 lbs.
Curb weight: 5314 lbs.

 

It's Been a while, BUT I can still rermember my father pulling a fully loaded 5th behind a '79 D350 custom automatic 4.10 geared 360 4bbl. Used to make regular runs between Wisconsin and Oklahoma with 3-6 salvage cars at a time. I know that they were built a lot better then, just a thought for all who say that a gasser won't do what a Cummins will. It just takes more time to get to speed and uses more fuel. The key is how often will the trailer be pulled. Daily, or every 2 months. Next time I have a chance, Ill post a copy of the last scale slip with my 1500 4.7. One thing though, Overweight fines are no joke. And no, I wouldn't buy a used truck from me, either

 

You might want to regear to 4:56's or maybe even 4:88's. And shorter tires. I would also debadge your truck. Why make it easy for a cop.