It is a common problem, and there are several threads on this, one that I started, but no problem.
You can just run a sawzall down the middle of the stake bottom, squeeze, then insert. You will have to run the cut line the full length of the bottom rail of the side rails. There are other ways, but this worked best for me. Take one leg off and use for a measuring stick, to see if you might have to make a cut in both directions. I had to do that with one set on one trailer.
If you don't do something to make them smaller, you will NEVER get them back out if you EVER get them in. This is what happens to those who hammer them in, when inclement weather "helps out" and they stick in semi-permanently. Don't hammer them in with a sledge! I have seen that done before.
The refurbished and reinforced M105s have a metal tab that runs on the inside of those wells that close up the gap so the old rails do not fit in.
It's a real pain!
IN some cases, the military has already reworked some of those deficiencies so a new owner might not witness it, or might notice one that is degraded more then another. Depends on what side rails they used for the install/mod.
Also, I purchased a all steel wedge from Steve6X6X6 at the Ga. Rally. The wedge fits in the hole, and opens it up with a sledge hammer hammering the wedge deeper and deeper into the hole. You would need a machine shop to make one like it.
Thanks to Steve!