It would be much easier if you decide to power the clock with a battery. You still can use the 12 V supply for three LEDs in series. (A small battery for the LEDs wouldn't last long.)

You won't need a PCB because you can just use the components' leads to connect them together. The schematic below should work for any common white LEDs you choose.

Hi Tracecom,

Thanks to both of you for the comments.
I understand the above schematic, looks good! But i have one (dumb) question... Where does the negative part of the supply go? (or is this the gnd?).

thanks

 

Where does the negative part of the supply go? (or is this the gnd?).

Correct. The negative lead from the supply becomes the reference ground.

 

Correct. The negative lead from the supply becomes the reference ground.

Thanks for the help Tracecom.
When i get some time i'll have a look and a think about how many LEDs i can get in there. As i said, i may have to remove most of the white plastic inside to fit the clock movement - which will in turn reduce my ability to fit the LEDs.
I may plump for 2 diodes - 1 to try to light the rev counts, and a second to light the airbag warning light (alfa romeo drivers will see the irony/amusement in this!).

Will post back when i come up with a plan
Oh, and (if im not back until then) happy xmas!