[Zabco]

Components used for securing loads do NOT have to be marked with their working load limits as do components used for hoisting/lifting loads (completely different set of regulations). However if not marked, there are tables in the FMCSA load securement rules that give maximum allowable loading based on size and type of material. Rules also give guidance based on type and size of load and type of vehicle it is being carried on what is required in type, number and positioning of tie-downs. If you are a bit familiar with what is required in the real world and know what real world size of components are then it isn't too hard to come up with scaled components that look correct. In truth, if your sample tie down link is for what I think you are trying to do it will probably scale up to much larger than needed in real world.