Were all dash vin tags riveted in place for 68 ? Was a aluminum rivet used ?
Reportedly, SOME (though VERY FEW) VIN tags in '68 were secured using large washer screws, similar to those found on roof rails and/or console to dash brackets of a 68.
I say "reportedly" because somebody posted this a year or two ago and I myself recall seeing it this way too but I cannot validate my knowledge by anything but MEMORY. My "memory" remembers it at least being a few 68 Ford PRODUCTS, meaning my memory might be on potentially any model Ford car. I believe it was on a 68 XR-7 if I were to "guess" since I know I swapped a 68 XR7 dash into a 67 Fastback I had back in the day and that "fits" inside my empty head.