I have access to a couple of sets of headlights from a 1998-2003 XJ8. Are these a direct swap for my 1996 XJ6?

 

You'll need to change the wiring plugs as they are different but the lamps are direct swap and possibly the best x300 upgrade. I've swapped mine last year and can finally drive safely at night.

 

The plugs are the only difference? No extra electrical ballasts or relays or such?

 

The two differences are:

1) Harness/Connector: As mentioned the connector from the headlights to the car's harness are different, so you'll either have to cut some wires and "rig" it up, or you can get some salvage harness from an X308 and connectors from X300 headlights and make an adapter, which is what I did.

2) Mounting Frame: The X308 headlight will usually juuuuust fit into the X300 headlight bracket/frame, but it is tight. The X308 bracket/frame has an additional cutout on the bottom to clear the rearrangement of the bulbs in the X308 headlights. If you are already getting some X308 lights, get them with the black plastic bracket/frame and swap the frame out with the headlamps.

....oh and one other difference, the headlight bulbs are different. So if the salvage X308 lights don't come with bulbs, you'll have to buy some new ones as the X300 bulbs won't work.

One final thing to think about is with regard to wear on the headlights. They are glass, but are a relatively soft glass and often look quite "sandblasted" after many years of use. The X300 hides that wear on its headlights fairly well due to the ribbed design, but the wear is very evident on the clear lens X308 headlights. So if that matters to you, keep an eye out for NOS or used X308 lights that have minimal wear then add a clear vinyl lens shield such as from Lamin-x to keep them from getting pockmarked.

Good luck!

 

I swapped them on mine, as suggested above with the whole units with brackets & X308 sub-harness, see the wiring colours here on reply 11

http://www.jaguarforums.com/forum/xj...so-far-195228/

 

I've done the swap as well. Head and tail lights.
As advised by Al, I swapped the entire assembly, Mounting brackets and headlights. This, you will find, is to better accommodate the change in the parking light position.
I didn't have any problems soldering the connector from the X300 light loom to the X308, I just did one at a time and found it fairly self-explanatory. You can find a good description of the procedure here. Jaguar XJ6; Jaguar X300; X308 headlights