Originally Posted by boober
Names boober-Just bought a 93 fleetwood prowler,30' and GVWR is 7400lbs. My question is how much vehicle do I need to tow it with.
All the pickups have a GCWR posted in the Owner's Guide. And most have a "tow rating" posted in their trailer towing guide.
Without more info, my answer would be you want as a minimum a 2011 or 2012 Ford F-150 with the EcoBoost (V6 turbocharged) engine and the Max Trailer Tow pkg (includes 3.73 axle ratio and telescoping trailer tow mirrors). That will meet your needs for "enuff truck" to tow a 7,400-pound TT as well as give you excellent mileage (compared to other half-ton pickups) when not towing. GCWR with the Max Trailer Tow pkg is over 16,000 pounds, resulting in a tow rating of 11,000 pounds or more for all cab and trim choices.
Next step up in capability and cost is the Ford F-250 pickup with diesel engine. That's an ideal tow vehicle for that trailer. Almost as good would be the comparable Dodge or Chevy 2500 pickup with diesel engine.
What size engine do I need but keep my mpg down?
For the best MPG, you want the smallest engine that has enough power and torque to tow your rig over the hills and mountain passes. That's the benefit of the EcoBoost engine. 3.5L size, but more torque and tow rating than the 5.0L V8.
Manufacturer's tow ratings are all overstated by a at least few hundred pounds. They assume that the truck has no options and the only payload in the truck is a skinny driver. But nobody travels that way, so I'd reduce the tow rating by at least 1,000 pounds when estimating the true capability of the truck. So for the EcoBoost Ford with Max Trailer Tow pkg, I'd not want to tie onto a trailer with a GVWR over 10,000 pounds. Since your trailer will gross 7,500, that gives you a wonderful cushion of fudge factor to be certain you're never overloaded.
For a tiny bit better MPG when not towing (but probably a tiny bit worse MPG when towing) then consider the optional 3.55 axle ratio instead of the 3.73. That means you cannot have the Max Trailer Tow Pkg with the telescoping trailer tow mirrors, and your tow rating falls about 1,500 pounds to around the 9,500 to 9800 ballpark. But that's still plenty of tow rating with a decent fudge factor for your 7,500 pound trailer.
Full disclosure: Right now I have a 2003 F-150 SuperCrew with the 4.6L V8 engine and 6,500 pounds tow rating. It handles my 7,000-pound cargo trailer just fine on the 6% grades on I-10 in far-West Texas crossing the three passes over the Rockies. But I've got the new-truck bug and will probably order a 2012 F-150 SuperCrew EcoBoost soon.