LED Panel Design. Arduino or other.

We are looking to develop a high luminosity through-hole LED panel comprising of a simple fixed text (8 letters).

The panel will be used in an outdoor racing environment. Tests on LED matrix panels have proven unsatisfactory in terms of brightness / visibility in sunlight.

In total there will be 267 LEDs split into the 8 letters as follows:
1: 36 LEDs
2: 38 LEDs
3: 38 LEDs
4: 42 LEDs
5: 34 LEDs
6: 22 LEDs
7: 22 LEDs
8: 35 LEDs

We are considering using 30000 mcd LEDs but will be guided by the developer:

1) All LEDs should be turned on or off at the same time (there is no scrolling / flashing requirements etc). Simply all on or all off.
2) The display should automatically turn off after x seconds with 10 second audible warning before shut off.
3) The design should minimise the amount of manual soldering required (e.g. avoid individual resistors for each LED if possible).
4) We require recommendations regarding power sources (e.g. 12v 6ah battery etc) and LED heat dissipation.

Price quoted is negotiable based on experience and speed of execution.