Start with an old pick-up. The one I used is a 1985 Ford Ranger longbed. Full size pickups work better, they can hold more. This truck was still running, but it probably would not have passed a smog inspection. I tried to sell it with no takers, so this looked like a way to get some fun out of it.
First step, remove anything that does not look like a trailer. Hood, fenders, doors, nose, bumper and seat came off first. The nose was cut off the cab with a grinder at the back of the wheelwell.
Once everything was unhooked from the cab, I unbolted it from the frame, then just pushed it off.
With the cab out of the way, I removed the exhaust, gas tank, and driveshaft. Then the engine was unbolted and lifted out. I reinforced an old swingset and used a come-along, then pushed the bed under the motor again so I wouldn't have to lift the engine again when I went to scrap it.
Next was the front suspension. This involved grinding off a few rivets as well as unbolting a lot of the components.
Same thing from another angle. The swingset I used to lift the engine is in the background, with it's reinforcing beam removed.
Next the frame was cut. I kept as much of the front section of the frame as I could to be sure I had enough tongue weight as the rear axle is centered under the bed, and the frame has a drop section which would have been annoying to deal with. Also I didn't want to build a whole new tongue assembly from scratch. I picked a cut-off point by measuring from a mounting hole on both sides to just behind the front suspension crossmember. It would have been a real pain to remove. I used the grinder again.
Next, I notched the flanges so the frame could be bent in to the center to make a tongue. I could have (and probably should have) just put a coupler on it at this point and called it done, but my brother said "maybe you could even make it dump", and that was just such a cool idea I just had to. The center tube is shown in place as I rough that in. The cut flanges were reinforced with gussets that were bolted in place, then welded. I also welded together the framerails, and reinforced them.
For the tilting part of the tongue, I made a "T" frame which pivots on a couple of 1" flange bearings mounted to the frame, since I had them on hand. I could probably just have had the tongue pivot on a bolt, since that's all they do for a snowmobile trailer. I used the u-bolts so I could slide the back end of the tongue sideways to align it.
I mounted the old bed-mounted toolbox on the cab mounts, and supported the front of it off of a frame that spans the bedrails. I also added the front running lights and reflectors and wired them and the tailight wires of the existing harness into a 4-prong trailer plug. The coupler and safety chains were also mounted. The red handle you see is the end of a hardened hitch-pin, which goes through three sections of pipe, one welded to each framerail and one in the center of the tongue to keep it in place when not tilted.
With everything ready to run, I went to my local RMV and registered it. Trailers under 3000 lbs don't require a title in my state, some states require homemade trailers to have a title and VIN issued. It's probably worth doing the research on the requirements before you start the project. Some states require that trailers 3000 lbs and over have brakes. If you need to add trailer brakes, it may be easier to swap out the axle at that point. A trailer axle would also have less drag than the truck axle, but since this is intended for short trips, I don't see a need on mine as of yet.
