The 9005 into 9006 simply means taking a 9005 (high beam) bulb and modifying the plastic base slightly so it fits into 9005 (low beam) socket...
There is a link on how to do it
http://www.bmwe34.net/E34main/Upgrade/More_light.htm
(this is for BMWs but it works the same way)
This is a great inexpensive and quick way to get more light (keep in mind that 9005s are not 'capped' like 9006s meaning more light goes forward instead of back into the reflector) so as I said in the other forum about lighting modifications in general - get your headlights AIMED after you change technology.
I used this technique (9005 into 9006) for 2 years successfully until I succumbed to full HID technology and bought the upgrade.
It wasn't cheap (400 bucks) but if you want the pure white headlights that the Audis, BMWs and Mercede sport, this is a way to go.
Some caveats here - do not buy a 'Xenon' or 'HID' like kit on eBay - there are plenty of these being sold. They work at first but the ballasts are made in China so not take the load for long.
Mine are genuine Phillips (Hella also distributes a kit) and they were installed by a professional (read PROFESSIONAL) shop - do not try this yourself. The wiring harness has to be modified since the HIDs do not use just a 12volt source to switch on - there is a relay and ballast that spikes the voltage up to fire up these puppies - and you don't want a shock from that. The pros know what they are doing.
And of course once they are in, make sure they do a headlight AIMING - the new HIDs shoot light in a different pattern and since you are installing them in a halogen housing designed for a 9006 bulb you will get not only whiter light but a larger pattern. You will like the new width for corners on country roads but you must have them re-adjusted DOWN so the new height of the beam does not blind the oncoming drivers.
Once you put them in however, you will love them and driving a car without will seem liek you are in the dark ages.
Also, HIDs run at a higher voltage but lower CURRENT than filament technology bulbs - basically they will draw 30 watts instead of 50 - but what you see is more of the whiter light of the spectrum instead of the yellow-ish tinge of older technoloigy bulbs.