I'd be starting with the bed from my 2008 Colorado, which is the motivation. Frame is rotted and won't pass inspection. I'd just remove it from the frame and have the rest of the truck towed to the junkyard or to the local auto program at the high school. Fabricating a frame is beyond my skill and interest. if there's something that have some adapter plates bolted to it to mount the frame, that would be cool. Re-use the brake lights as designed. Obviously it would be hilarious to keep the same wheels, but I don't want all the weight of a the truck axle, differential, and who knows what else due to the 4WD parts. And brakes I wouldn't be using, so. This would be towed behind a modest CUV, mostly likely. The homebuilt trailer regulations in RI seem manageable, but I haven't found the exact safety inspection details yet.