“Well we know that if various cars were ordered under the same DSO they should all have originally gone to the same area and likely all order by the same dealer.”
If we look at the VIN’s in question here, we start with one ending in 318 and conclude with one ending with 491; so a potential of about 173 cars in the order.
“In that case a right hand drive car would not have been legal for that country.”
Sweden had legal left-hand traffic (USA has right-hand traffic) from approximately 1734, well into the 20th century, despite the fact that virtually all the cars on the road in Sweden were LHD. (One argument for this was that it was necessary to keep an eye on the edge of the road, something that was important on the narrow roads in use at the time). Also, Sweden's neighbors Norway and Finland already drove on the right, leading to confusion at border crossings. This not withstanding a right-hand drive car was not “illegal”, and in some cases might have been “more natural” in a left-hand traffic environment like Britain’s.
In 1963 the Swedish parliament passed legislation ordering the switch to right-hand traffic. The changeover took place at 5am on Sunday, 3 September 1967, well after the 1966 Mustang model year.
“Can agree for sure that the box (if marked correctly would have been for right hand drive - remember these sheets were used for allot of different car models - not just for Mustang.”
Some Ford vehicles were known to have been assembled as right-hand drives; the Cortina for one. It may be possible that the build sheet was composed to be utilized in those instances as well.
“Think is a long stretch with a number in a box and at least four different possibilities. Given it was likely ordered for Sweden I think is highly more likely that the 5 represents a change in the lights since that is something we see often (as a higher requirement) on European delivered Mustangs
The omit seal beams is odd as I'm not sure where (country) or why seamed beam headlights (if that is what ST beams is referring to) would be illegal in any specific country in 66 unless these same build sheets were also made for use in other countries were Fords were built that year - a possibility IMHO.”
Your statement here prompted me to do a little more research. Most low-beam headlamps produce an asymmetrical beam focused for use on only one side of the road. Headlamps for use in LH-traffic countries have low-beam headlamps that throw most of their light forward-leftward, while limiting the light range forward-rightward; the beam is distributed with a downward/leftward bias. Headlamps for RH-traffic countries have low-beam headlamps that throw most of their light forward-rightward, while limiting the light range forward-leftward; the beam is distributed with a downward/rightward bias. The beam thus lets the driver see obstacles and road signs on his own side of the road at a safe distance, without blinding oncoming traffic. The LS LAMP in this build sheet category might refer to the readjustment of the headlight beams to the left side. This would have been necessary for Sweden’s left-hand traffic pattern at the time that the Mustangs were delivered. When the traffic pattern in Sweden changed in 1967 to duplicate that of the USA’s, it likely meant that Swedish headlights had to be re-adjusted.
So, the 5 code we see in this box might certainly mean that the headlights were adjusted for a left-hand traffic pattern. Still, it’s curious that there’s a special notation on the bottom for an otherwise basic 22:1 steering box. And there are some strange codes for the springs and shocks on this particular export as well….