Brent,
  I think it will be difficult to measure the improvement numerically
because, as I understand it the differences in the two systems are more
about the distribution of the light than about simple brightness.  In
principle maybe, on a very dark road, one could walk around with a light
meter and distance measuring devices and gather lots of data and then plot
it on graph paper.

When I did my headlite relay upgrade I checked the brightness before and
after using a Gossen Luna Pro meter left from the days when I took
photographs with an antique Leica camera.  In a dark garage, I blocked off
one side at a time and then, at a set distance, moved the meter around to
find the highest reading, in EV as I recall.

My wiring changes started with a 30A fuse holder attached at the positive
battery terminal and then a hefty wire running up to the space behind the
grill near the headlites.  I mounted two relays there, one for high beams
and one for low, and attempted to protect them from the weather.  I also
grounded the lights to the body near by.
  This gave a measurable and visible increase in brightness.  I also then
changed the bulbs from the standard 9004 to the enhanced brightess bulbs
from the FLAPS, from Sylvania I think.  Of course when you get more lumens
from the same watts you pay the price with a shorter bulb life.  Over all I
got brighter lights, but of course, no improvement in the distribution of
light on the road.

Are you planning to go with the South African grill, etc. or simply go back
to the '84 grill and lights?

Good luck,
Larry A.

On Wed, Apr 6, 2016 at 10:14 PM, Brent Weide <brent.weide@gmail.com> wrote:

> Folks:
> I'm about to embark on the upgrade of the 1991 square 9004 headlights to
> the early vanagon H4 round headlights and would appreciate  your
> assistance.
> Does anyone know of a way to accurately measure the improved lighting using
> every day tools?  I'd like to measure that headlight strength before and
> after the change.
> I'll be documenting the change (good or bad) on my website and appreciate
> your feedback.
>
> All the best,
> Brent
> --
> Brent Weide
> Portland, Oregon
> www.weidefamily.net/vanagon/
>