After testing quite a number of LED bulbs, this was the best combination I found.
It uses 5 x 5050 SMD LEDs for the bayonet bulbs (fuel, water, oil and tachometer) and 1 x 5050 SMD LEDs for the wedge bulbs (speedometer). All sourced from Ebay. The light output from these is about as even as I think I can get it.
The tachometer is dim across its face because of a design fault insofar as there is no diffraction ring around it. However, I can see the end of the needle and all the numerals so I am OK with it like this.
The speedometer has a different hue from the other gauges because its diffraction ring is clear instead of translucent blue. I don’t know why the ring is clear on the speedometer and blue on the ancillary gauges. I am going to try to source a blue one and if I can’t do that then I will tint the clear one myself.