Welcome to the club and congratulations on your new (to you) Sunline T-2475.
Wrt the tow vehicle question:
A lot depends on the type of towing you plan to do, the amount and the locations, such as long trips, lot of hills / mountains, etc. The more trips and more mountainous driving, the more truck I would look at.
Also, remember, the published tow rating only includes the driver. Therefore you have to reduce the tow rating by the weight of other passengers and cargo you plan to have in the truck when towing to know what the realistic tow rating is of the F-150.
For example, if you plan on doing a lot of long trips that include a lot of hills / mountains, I might also be looking at the 5.4L engine, just to know I had the extra power to handle these conditions.
To respond to your specific question on the F-150 w/ 4.6L & 6,100 lbs tow rating:
The first check that I use is the 80% check. Based on having your loaded trailer ~80% of your tow vehicles towing capacity. This 80% rule gives a buffer to account for cargo and driving conditions, such as towing in hills and mountains.
In your specific case 80% of 6,100 lbs is 4,880 lbs.
I would guess that with a trailer of 5,500 lbs GVWR; your loaded weight would be between 4,500 lbs and 5,000 lbs.
So it looks like the Ford F-150 with a 4.6L v-8 with a gear ratio of 3.55 is in the ball part, at least from the initial assessment.
However, as I mentioned above, I would also look at a 5.4L engine. The 4.6L could do it, but you probably be smiling a lot more with a 5.4L.
To do a full weight analysis you need to know or find out:
For the F-150 Tow Vehicle (TV)
Gross Capacity Weight Rating (GCWR)
Gross Vehicle Weight Rating (GVWR)
Unloaded TV Weight
Loaded TV Weight
For your Sunline Travel Trailer (TT)
Gross Vehicle Weight Rating (GVWR) (5,500 lbs)
Unloaded Tongue Weight
Loaded TT Weight
(estimate at Unloaded Weight + 800 to 1,000 lbs depending on how much you carry)
Loaded TT Tongue Weight
(estimate at Unloaded Tongue Weight + 300 lbs)
The TV GCWR > Loaded Truck Weight + Loaded TT Weight
The TV GVWR > Loaded Truck Weight + Loaded TT Tongue Weight
The TT GVWR > Loaded TT Weight
The other weight to consider to make sure youíre within its limits is the TVís Gross Rear Axle Weight Rating. This would be compared against the loaded weight of the truck on the rear axle plus the loaded tongue weight of the TT.
Hope this helps some.
Mary & Tom (aka Hutch)
2015 Jayco Eagle Premier 361REQS
2014 GMC Sierra 3500HD 4x4 CC D/A
Sunlines: 2005 Solaris T-280SR; 1999 Solaris T-2670; 1998 Saturn T-24A