That's a very clever method Jadran, thanks for the tip!
Sadly, I already ordered bright white LED's intended to replace the backlight of my cluster. The Del Sol uses T5 bulbs for everything but the fuel warning, so they fit into the indicator sockets.
The problem with this approach is the colour of the indicators, red comes through as pink, and green is very bright.
If anyone is considering swapping the bulbs, I'd recommend Jadran's method. It's slightly more complex to fabricate, but the colours will be right, and you won't have to solder directly onto the original dashboard wiring.