Hi All
First concerning the issue of left or right dipping or which side of the road are you driving on. Logic says that the bulbs should be different, which will take some research are seal beam head lights numbers for North America different from the UK and Australia?
The observation from my testing with different pre-focused blubs is that they don't seem to dip down to either side they are much more up or down. With the prefocused Halogen bulbs I was using 6v 35/35w P15d-30 APF Base #170-756H from Classic and Vintage Bulbs, Blackwood South Australia
http://www.classicandvintagebulbs.com/ I suspect that if there was any down and to the side for low beam that they would have been down and to the left. But from my test picture the change in pattern from hi to low is minimal. The photos in first post came out wrong way around. This picture is the high beam for alignment purposes the orange line on the floor is running just down the right side tires. Halogen left regular prefocus right, as you can tell from the hood in the foreground this was taken sitting in the drivers seat.
The photo below was actually of the low beam alignment.
Now to Harry observation about what number bulb I was using and 6v or 12v. Harry you were right on the money the bulbs that were in the black out units when I got the units were 2326 12-16Volts and the ones I was resoldering base on are 2331 6volt.
If I were driving my trucks a lot at night I would go back to the Halogen even with the shorter life they are brighter and whiter light.
Cheers Phil