Thanks for the help to all. This is an incredible website for someone like me. A little short on knowledge regarding these things but willing to try. I got the latch working. Mine has no o-ring on the small end, that I could find. Just a large o-ring on the fat part of the pin. After getting the pin to slide a little easier, I started messing with the latch alignment. I loosened the bolts where it attaches to the cab just a little so that with persuasion I could tap it around a bit. I got it into a better seated position and voila, the pin magically slid in. Tightened it up and it continues to work. Now for the headlights. I couldn't find a TM for the FMTV so I am using the LMTV TM. Seems to be the same, sort of. Symptom is no headlights when the switch is in the low beam setting. After a bit of time the breaker kicks off. I pulled the bulbs, they test out OK. I checked continuity between the bulb wire sockets and the ground wire socket. I assume 91 is ground. Got continuity on the socket that is supposed to be high beams, number 17, (left side looking into the bulb assembly), both sides. I assume now, I am looking for a bad wire issue, but why on the high beam wire, when the low beams aren't working? Suppose I should check the wire sockets and look for current to verify which one is hot with hi or low beams. Is there an electrical schematic for this somewhere? I've searched, but can not find one for the FMTV.
On a different subject, I found some breaker fuses on line that look like the original, but they are 12 volt. Is there any problem using a 12 volt fuse where a 24 volt fuse belongs? My truck came with a 24 volt fuse stuck in a 12 volt circuit, which I corrected. Thanks again to all who have helped, I am new to this adventure and this forum has a ton of good info.