I 've been wanting to put together a pickup-bed utility trailer for a while. After finding a playworn no-name Chinesium wooden livestock trailer and stripping it, I added Greenlight wheels/axles out of a junker travel trailer that I will be converting to a fixed storage shed, and added a toolbox and spare tire from my parts bin, to make a trailer out of the bed left over from my C30 wrecker build.
This tows well behind lifted or stock height 4x4 trucks, not so much behind lowered ones. Someday I'll be 3D modeling/printing a proper truck bed trailer chassis with tool box and spare wheel mount, that accepts Mattel, M2 or GL wheels to make my excess pickup beds useful.