One aspect of an older Ford/Camper lashup is Ford's famously flexible frame. (This is National Alliteration day, isn't it?) During the 1990's, and by design, Ford's pickup frames flexed and twisted a LOT more than its competitors. It was actually a small addendum to the suspension. This is why campers on Ford's must have more cab overhead clearance so as not to come into contact with the cab roof.
Because of the flexing, there is a chance that one of the four 3/8" hardened bolts holding the bed to the truck frame has come loose or overcome its welcome with the surrounding sheet metal. This has happened to me a couple times now and I keep patching it up with larger and larger fender washers hoping to get a few more years out of the connection. With my Dodge hydro formed frame and on a short bed truck there is very little twisting/flexing. So, when I see one side or the other of the camper overhead seem to have more range of motion than usual, I instinctively head for the usual suspect: the pass side front bolt on the truck bed for an answer.
About tie downs: you need to have adjustability. There is a 'sweet spot' at which there is enough tension to keep the box on the bed, but not so much as to pull your camper apart. Neophytes invariably apply too much tension to the tie downs. For me, this is an on going situation, depending on how much the axles are twisted up and transferring that twist through the suspension to the truck frame. I suspect you will set and forget if you are staying off really bad roads. After putting the camper back on the truck for the next trip, I manually check the tie downs at intervals to see what has changed and readjusting the tension as needed (PRN).
One more thing. A good bet to keep your camper centered in the bed is some kind of centering system. I use the Lance Camper Centering Guides because that was what was available 15 years ago, and have had great luck with them. I've seen some much improved versions made by our own on this forum. When the camper shifts, side to side, it puts undue pull on one side's tie downs, and loosens the other side. Over time, this is not good.