Still a bag full of surprises?

The 131S is surely full of surprises even at this age. CKD and assembled in Johor Baharu way back in 1977, it was FIAT first 131S model here in Malaysia (that's how old she is!). Last two weeks she was chugging along with three cylinders. Equipped with the little knowledge on Fiat (131 in particular) that I have and phone calls to a couple of helpful mechanics, I tried to diagnose the problems. It seems that the fourth cylinder is not firing consistently thus irregular firing of spark plug. The recommendations :
1. Change spark plugs - did that with Champion N9YC - same firing.
2. Check the high tension lead - done that - no visible and audible results.
3. Check the coil - did just that and even better by changing to a Bosch unit - again no result.
4. One of the valves could be faulty thus resulting in irregular firing of spark plug - I am no mechanic.
5. Called up one of the helpful mechanic again.

He actually drove the car back to his workshop 10 km away. It was later diagnosed as having a faulty distributor - the whole assembly, contact point, condensor etc.

Lesson learnt:
In maintaining a classic car such as mine (classic or antic?), it is advisable to keep stock of essential parts that are considered as maintenance. You never know when you will need it. I used to get second hand parts (extremely difficult to get parts or rather expensive to buy it new) from this Indian chap in Kg Nakhoda (on the way to Hulu Yam).
A couple of shops in Jalan Ipoh still keep a healthy stock of parts (haven't seen them for quite some time though).