There are two types of "nose cones for these military cucv starters (orig oem type) Some you use a Shim with and some you don't. On the ones that you are NOT suppose to SHIM, it says so. Look closely at your #3 picture, stamped on the nose cone that the solonoid is bolted, I believe I see "NO SHIM"-- I'll bet that if you look right above the lettering stamped on the alum it will also have a letter "A" stamped on it. All of the "A" type sayes "NO SHIM " . Also a lot of these types will have stamped "DO NOT SHIM" in the flat area between the two bolt holes.
There is the other type that does not say whether to shim or not. If you will look at the same area where you found the "A", on these there will be a "B" stamped (or rather cast into the housing. Hope this helps.