There is an old CAT Shop Notes tip that recommends 1446 bulbs for a little brighter incandescent bulb. They are available on ebay and some model railroading shops.
It is a 2.4 watt bulb vs. the 2.2 watt Lucas bulb. So about 9 % brighter, all other factors held equal.
My dash is out of the car so I cannot test it directly in driving conditions. But on the bench in a bulb holder, it did look meaningfully brighter than the stock bulb set up next to it.
One thing I noticed about the stock bulb, original since 1967, was that a slight film had built up inside the glass. Probably from the filament vaporizing over time. That is going to make any original bulb give out less light over time, the older it gets.
What really made my tach
tremendously brighter with a stock bulb was to repaint the inside of the can a fresh gloss white when I had it apart. The white was starting to dull, crack and flaked off in a few places. Forget trying to balance the light with half white and half blue. It now is easily twice as bright as any other instrument.
While a creamer looking can interior back side paint may make a LED light more pleasant, I am not sure what you would give up in brightness. Only way to know is to try it I guess.
Anyway, my own next step it to try and repaint the interior of the other instruments a fresh gloss white. Now if I can just figure out how to get the other gauges apart without ruining the bezel...
Gene