In my experience i have found a slight fit problem with the drivers side LHD inner front wing, which i believe may be from build differences. This manifests itself with the outer/upper edge of fibreglass inner wing flange not following the shape of the inside of the aluminium outer wing correctly. Even with the sealing rubber attached to the fibreglass edge, it did not seal against the aluminium cleanly. To improve this, i felt the inner-wing panel needed to fit further into the car, thus improving the relationship of the two surfaces to each other, but by doing this it closed the gap between the intermediate steering shaft and the panel. Hence, improving the fibreglass relief around the column. As to the early conversion, i have always been reasonably happy with the column height, basically because of its exit position from the dash panel not really giving a great scope for change. However of removal of the Ford switchgear column for replacement with the early style simple column, as supplied, i found the column outer tube end struck the accelerator pedal, the simple upper fixing was not good enough to support the column tube safely, so an extensive lower bracket needed designing and fitting. Finally, because of the cars original set-up the inner spline shaft didn't work in the new configuration, requiring the design and manufacture of a completely new inner shaft.
As to why a standard early RHD specified column assembly wouldn't properly fit the LHD i cannot truely say. I suspect variances between the cars, manufacturing changes as the model progressed, and a number of small detail changes that you are always likely to find on a small volume hand built car.