Hey Christiaan:
I just did mine yesterday, for the hell of it. I tried to read the posts and what not on TNX, but it was confusing the crap out of me with all of these people trying to buy a new fitting/nipple to fit into the axle housing.
I simply removed the dust cover from the nipple that's already there, slathered the nipple up really good with some RTV, slipped a 3/8 inside diameter fuel line over it, and clamped it down good with a hose clamp. It's on there super tight and isn't going anywhere.
I ran the hose up to the rear taillight and installed a cheap fuel filter on the end, attached with another hose clamp.
In total, I spent about $25, because I had to buy the RTV and hose clamps along with the fuel line and fulter. I think I paid about $10 for 8 feet of fuel line (which was plenty enough, and left me enough to put a huge loop in it before the axle), $5 for the filter, and $4 for a pack of clamps and $6 for a tube of RTV.
The hardest part of the whole project was slipping the existing dust cover off of the nipple. Took a little coaxing with a flat screwdriver, but only took a minute or two. The whole project took about 15 mins.