I just bought this 2006 F250 4x4 diesel and I am looking for a Tool box that will fit inside the bed under the rails? I will be towing a 5th wheel also if that makes a difference.
Thanks!

 

I have no problems with my 2015 crew cab long bed with a side to side tool box that sits 5" above the bed rails. I use the Ford in bed hitch system with the Ford/Reese Elite 25K hitch.

check places like Northern Tools, Lowes, DeeZee, etc

 

It's miss leading to have him think that an obstacle sticking 5" high in your truck bed will work for his.
Hitches, truck height, trailer height will play a factor not counting the terrain where ever the truck and 5th wheel go. I have almost 7" between the 5th and bed rails and there was 1 spot in a turn/ low spot that it came within 2 inches.
As Just Stroking said for purchasing a box almost anywhere, the key factor is what you feel comfortable with sticking up. I also have a box in mine but it's only an inch or so above the rails.

 

I said what I have in mine...and the hitch...and that it works for me....i never said, nor implied as you seem to think that i did, that it will work for him also.....

and I never said you can purchase anywhere...i suggested a few places to check....it will be up to him to check the box dimensions and his trailer to verify if it will work...these online places will give him physical dimensions, LxWxH so he can measure...this saves gas and time over going to places to actual view them.

He will need to set his hitch height and pin box height correctly for his vehicle to tow the 5'r before he can determine what tool box will or won't work...so, don't assume that i was implying anything nor telling him where nor what to buy.

 

I have a 2015 F250 long bed with FW hitch set up from Ford. Go to Tractor Supply & they have what you want. I installed it, fits under rails & cover goes over the box with no problem.

 

i have a weatherguard 664501 in my 90 f250 that i pull my fifth wheel with. not the cheapest, but one of the best aluminum below the rail box's around. i don't hesitate to stand on it[im over 300#], can't say i would do that on the junk they sell @ lowe's, or the parts stores. i have used this in 2 trucks, 6 ? years.

 

I bought a dewalt 36" wide tool box on clearance for 80 bucks and have the handles chained to the front tie down loops. its below the rails. if it gets in my way when I transport a large motorcycle, I move it behind the drivers seat and sit it on the fold down cargo floor on my 60/40 rear seat. the 6 draws and top storage area in the tool box are great. just throwing this out there...it works for me.

 

Thank you everone for your reponses!