Adding reciever trailer hitch to semi frame

You're also going to want a brake controller, properly wired lighting, and a spot to hook safety chains onto.

 

You wouldn't be able to use the truck's existing trailer wiring for stop and turn signals.

The 7 pin round plug on the truck has brake lights on their own circuit and the left & right turn signals each have their own wire.

On the 7 way flat pin RV plug the brake lights are powered through the turn signal wires. Constant power when braking, flasher interrupts the constant power on the side you activate the signal on.

Newer trucks the tractor lights are normally controlled by a module, so splicing in to the tail lights could cause the module to think you've got a short or ground in the brake/turn signals with the trailer connected. Just some things to think about.

 

If your towing a travel trailer or a utility trailer just have a 7pin female plug wired into the trailer and just use the tractor power cord. Only thing is you won’t have any electric trailer brakes.

 

No need to replace a cross member.
We just took a big piece of 1/2inch or so flat plate. As wide as the frame and as tall as you need to get receiver height where you want it.
Couple tabs welded to the side of it to bolt to the frame and a few pieces of square tube from bottom middle of plate to the outside of frame rail as gussets of sort. Pretty easy. Take it to a welding shop.

And wiring harness will take some doing like amodel said

 

I bought a set of magnetic tow lights and made my own 7 to 4 pin connector for the tow lights. So much better than splicing into the wiring which will most likely cause an issue later down the road. I only pull a 4k pick up with it and I don't have any brake controllers installed. Also, with the receiver I have (the one linked above) just bolted on to each side of my frame. I didn't install, nor replace any crossmembers.

 

I did just this and tried to post pictures but can’t seem to. So far as wiring harness, on the rear at your new piece of plate or what ever, place a new 7 wire plug. Splice into your existing wiring harness for the rear brake, turn and park lights. Solder in and wire into plug. Install a brake controller on dash and run the single wire back to your new 7 wire flat plug, to the terminal that coincides with trailer brakes and you are done.
When pulling off of 5th wheel use regular trailer cord. When pulling off of receiver, plug trailer cord from tag along or in my case goose neck, into new plug and truck on.