I've just replaced my (excellent) HTC Desire with a used HTC Desire Z (slightly slower CPU, but oodles more RAM and also a real keyboard).
I wanted a proper car dock for this thing (like my old Desire, I can sort of jam it into my dash between the side of the gauges and the mileage-reset-pin, but I'm sure you'll agree that that sounds rather dodgy).
The thing is:
* Most "official" docks don't have a built-in power lead, you'll have to fiddle with the lead every time you (un)plug it. Daft.
* One of the few docks that does have a built-in power lead gets consistently poor reviews about that very item. I don't want to pay for a poor solution.
Over at XDA
, they've been experimenting with using a dock for a Motorola Droid X with pretty good results, so I thought I'd try that. This is my documentation.
Here's the box it comes in, so you know what to look for if you want to do the same.
Only one problem: the micro-USB connector is the wrong way round, with the "narrower" front of the connector outwards. The Desire Z has its micro-USB socket with the "wider" back towards the display. So that connector needs a 180 degree turn...
First off, pull out the insert (it's intended to be used unless you've got a case around your phone) and remove the four screws from the back.
On the top, use a blade to unlock two small notches. Then, the dock should come apart quite easily. Don't worry about loose objects or projectile springs. :-)
Inside the bottom part, you can see just how easily-modifiable the connector is. Thank you, Motorola!
All you need to do is gently pull the connector out of its little cradle, twist the cable a little extra (or a little less, if you prefer), and prod it back into the cradle.
Then just snap the front cover back on, tighten the screws, reattach the insert, and you're set!
I've just confirmed the power and data connection when I uploaded these photos. The back of the dock has an exposed micro-USB socket where you plug in the 12V charger -- or a USB cable to connect to your pc. Thanks again for doing things right.
The charger is apparently overclocked -- at least, there's one of those annoying blue LEDs in it that is always lit, even when the car is off and the phone is not in the dock. All it does is illuminate a clear window with the Motorola logo etched into it.  Hrm. That will have to go.
Luckily, the fastener ring that holds the window in place is easily removed by jabbing a screwdriver at the indicated notch.  The LED is then exposed , so I turned it sideways and covered it with a bit of black electrical tape. After reassembly, I lightly filed the inside edge of the handle ring, not that it was really necessary. Now, I have neat grab-o-handle for unplugging the thing without yanking at the cable  (and providing me with a handy excuse to not trim down that excess size).
I may further update this thread when I have more on-the-road experience with it.