I've heard anywhere from 4-6 thousands some include the box some you supply the box,used of course. Make sure you get it done where they will stand behind their work.
As I type this I'm having problems with my truck that I bought already stretched. 05 Petebilt 387, 22 foot box, Cat C15, 10 wheels. Empty with fuel tanks at 1/2 full I scale at 12,160 pounds. With 8 pallets at 10,300 pounds, loaded to the rear door, I scale at 39,660 pounds Gross weight. Im register for 44,000 pounds, so that is ok, but my drives are at 13,380 pounds. My front axle is rated at 12,000, GGRRRR. Monday I will have to install 16 ply tires that can carry 14k pounds. But I still have to content with the axle.
I have four options. 1) move fuel tanks back 2) move drive axle forward 3) add pusher axle 4) install 14K axle Pusher is out of the equation for me. So that leaves front axle, fuel tanks or drive axle that has to move. All three will cost downtime and money.
That is why I said make sure the shop that does the work stands behind it. Mine was done 4 years ago by the previous owner who never had a problem running that way. According to him it was never a problem at the scales. I don't like running that way so I will fix the problem or sell the truck and inform the new owner of the issues.
Good luck with your build, It is a great running setup.
