If your stop and tail lights are like candles at the back of your classic, replacing them for brighter LED ones might not be the solution. You might be told in some cases that because your vehicle is positive earth, you cannot fit LEDs – yet there are firms out there saying that their lights are bipolar. What does all this mean? Well…
LEDs are unipolar devices – ie, they will only pass current one way. However, a bulb described as bipolar has a built-in bridge rectifier that automatically sends the current through the LEDs in the correct direction. So any lamp described as such will be suitable for your positive-earth Austin. The dim lights may well be due to poor connections and earthing, or aged and oxidised wires. Check these over before investing in an expensive set of LEDs.