Square Body Tow Hooks - 3 Options?

[Ironhorse]

Ran all three sets of tow hooks thru my bead blaster recently, primed and painted. Large J hook and center S style hooks belong to my BIL, member old wagon. The large J style hooks to the left have the letter " U " showing on the shank of the hook. No lettering, marks or part numbers at all on the center tow hooks which are normally found on the 81-87 trucks. Again find the letter " U " on the shank of the far right hand tow hooks. Still a bit of a mystery on these for me. This is only the second set of this style I have ever run across. Part numbers of 14029218 & 14029217 on the large right hand hooks. 328072 number on the " J " style hooks. NO numbers or marks on the " S " looking hooks but same hole spacing with larger diameter hole on the large right hand hooks. Appears they will bolt right up to the 81-87 frames as they match bolt locations. Sure would like to know just how these were made available and on what trucks specifically.