OK, after almost a year and several pleading threads waiting for someone to post the dimensions for the roof rail extension drill guide while in the meantime watching the rails I had bought (eBay $70) gather dust, I decided to pop off the rear interior valence panels and see what exactly I would be dealing with.

On the basis of what I saw/measured, I decided to try and make my own guide out of whatever I could find at the local Lowes.

Here's what you need:

8-10 3/8" fender washers
1 - 3/8" OD, 1/4" ID spacer/bushing (3/4" I think)
3/8" heat shrink tubing
glue/epoxy

Step 1: Shrink 2-3 layers of the tubing on the spacer/bushing until it fits snugly into the fender washers when they're stacked up;

Step 2: Put glue/epoxy on each washer (I used 5 minute J&B clear), stack them up, then put the bushing/spacer down into them, making sure that the bushing also gets a little glue/epoxy and that it is at 90 degrees to the washer all the way around;

Step 3: Put another 1-3 layers of shrink tubing on the spacer/bushing nub/nipple sticking out, testing after each layer until it fits snugly into the hole on the interior roof frame (a bonus here is that once it fits snugly you won't have to hold the guide in place while you drill;

Step 4: If needed, grind down the nub/nipple until the fender washer face sits flush on the circular spot on the interior roof frame (and the nub/nipple is not touching the roof itself thru the hole); you can also add washers as needed to achieve the same result.

Attached is a picture of my completed drill guide.

It worked great: the holes lined up perfectly with the rail extension.

I used a 7/32" bit to drill the guide hole as opposed to the 14mm (5/32") bit specified in the instructions. I am guessing that as long as this guide hole bit is smaller than the pilot bit on the hole saw drilling from the top down, then the hole saw won't wobble or otherwise walk off-center.

Similarly, I used a 32mm hole saw (1 1/4" I think) instead of the 34mm spec'ed. Lowes only carries a 32mm and a 35mm in their Cobalt brand, and I figured it would be better to start a little smaller than larger on the theory it is easier to take a little more metal off than try and add it back on. The 32mm worked fine, and the holes it made didn't need to be enlarged at all.

Lastly, I treated the holes with some rust preventative and then some clear coat touch up since I couldn't find any silver touch-up paint that matched the D2.

We are using those clamping type, low profile roof rack cross-rails with a key lock, the 54" long version ($35-50 on eBay). See picture.

As they are low-ish profile, if you're not careful about cross-rail positioning, they could interfere with the operation of the rear sunroof (and maybe break it?), so we marked on the rails where the "no cross rails zone" is on the rail extensions (see picture). One mark is about 4" from the back of the rail and the other is about 21" as measured from the rear seam in the extension rail. There is no problem with clearance of the front sunroof with cross rails position anywhere on the front rails because of the shape of the roof.

Hope this helps someone out there.

 

Sorry to resurrect a dead thread, but I wanted to take a moment and thank you for this write up. Just installed some secondhand extensions on my Disco after making a guide as you outlined. Everything came out perfect!

This ownership group is great.

 

Glad to help. I get so much help from this forum that I am glad I was able to pay it forward just a bit.

Those original drill guides are the most unobtanium parts I've ever sought (and I have seven vintage Porsches, so I know what unbotanium parts are). Never even got a confirmation on this forum that they even existed (even though the rail extension install guide references them).

BTW, isn't it crazy that LR didn't just make the full length rail setup standard. I have a 2004 that came with those manly-looking but otherwise useless fat tube half rails, and I am so glad I replaced them with full roof length skinny rails that actually make the roof useful now.