I can no longer see my instruments at night and want to replace the dim, 50-year-old original 3W bulbs with T10 5W LEDs. I've just ordered LEDs with the same dimensions (diameter 9.9mm, length 24mm, base width 9.3mm)so they'll fit into the instrument holes, and I ordered a dimmer on eBay in case these are too bright. I long-ago by-passed the original rheostat, which was getting cranky. It wouldn't work with the LEDs anyway, as they are not subject to voltage control.

From the looks of things, power comes through the rheostat, now bypassed, and the bulbs are wired in two legs, branching from one of the speedometer bulbs. The heater control light is included in this chain, with all lights being individually grounded to the metal of the dash. Does this individual grounding make this a parallel circuit?

I'd appreciate any advice I can get from anyone who has already upgraded their panel lights, including they types and P/Ns of the bulbs they have used. If my experiment succeeds (not sure yet how to reach the bulbs for the two temp gauges), I'll report back with details.