Hi Martijn, it certainly is possible, like many other on the forum, I've changed all mine for LEDs, with the exception of the headlamp bulbs, as in the UK, it is illegal to fit LED bulbs to units that were not designed for LEDs in the first place. Here's a link to the people I and many others have used:
https://www.classiccarleds.co.uk . If you are changing the indicator bulbs, you will need to fit this
https://www.classiccarleds.co.uk/pr...-classic-car-with-oe-click-x-l-p-2-3-pin , if you don't the indicators will flash too quickly.
Good luck, the company is very helpful and will answer queries over the phone. Fitting LEDs is an incredibly worthwhile mod, in my view, virtually essential in an older car such as yours, with very small and probably by now, rather dim bulbs.
