For future reference, if you are able to you should attach pictures of the part you are trying to figure out. On a lot of these trailers, they are what sometimes gets referred to as "trailer salad" or other such names, with the point being that just because the model says one thing, it doesn't necessarily mean every part of the trailer is that specific model.
For example, the M101A1 model refers to the trailer bed itself. Usually it will be installed onto the M116A1 trailer frame, but not always. It's not uncommon to see the A1 trailer bed on the A2 trailer chassis, or the A2 trailer bed on the A3 chassis. Or sometimes the reverse, the A2 bed will be on an A1 chassis.
When these were in service, a lot of motorpools cared less about keeping everything exactly how the manual says, and would take parts from multiple damaged trailers to make one complete one, and bolt the rest together to turn in for replacement.
Just to say, the model number is just a starting point for where to find parts, but if you're asking for assistance pictures are extremely helpful.
The 9/16 lug nuts are for A2 and A3 trailers with the 8 bolt GM wheels on them, the A1 is supposed to be a 3/4 lug nut and directional on each side, with a 5 bolt wheel like the 2.5 ton trucks used. (EDIT: 5 lug not 6 lug wheel)
