I just hooked the DICE up without its case and made some measurements and to confirm I had the right pins.
Yep it all looks good - Ive updated the image with markings for the pick up points for the blinkers and the power supply.
Ill hopefully get a chance later today to solder the Arduino in and give it a go.
The multiplexer (74HC151) second from the left is the chip we need to attach to.
Pin 1 Left blinker input
Pin 2 Right blinker input
Pin 16 +5V
Pin 8 0V