During the original (rushed) build I removed the sensor for low engine oil level from the block and tapped a wooden round peg in the round hole. Now, during a rebuild I have more time to consider... should I  properly seal the hole, which kept weeping oil .. or reinstate the oil level warning sensor. To be honest I am thinking that it is not needed and just one more thing to leak or go wrong and I am not sure if it is just a single point sensor or a gradual sensor. So before I throw it away I was wondering if anyone else has fitted/used this sensor and has some experience to share.

Didn't think Pintos has a low oil level sensor. It'd need a lot of oil in it to bring the level above the sump to the block.

The hole in the block is about 1/2" diameter on the offside near the mounting arm but right down just above where the sump starts. The sensor is then quite long about 6 inches roughly, a long thin metal probe with a wide "bung" at the top where the sensor wire exits to a connector. When the "bung" is in the hole the end of the sensor is then down in the sump at a similar depth to the end of the dipstick. 

Her is a photo of one thats for sale on the web.

My dipstick also has that sensor.

As far as I can tell it is a small heater and a bimetalic switch. The oil keeps it cool, no oil and the switch opens and a light goes on in the dash.

I never wired it into my home made loom but still use the dipstick which goes almost vertically into the sump near the starter.

Ah, I was wondering how it might work, floatation seemed unlikely, I thought perhaps a change in capacity between two plates, but a rise in temp is a good possibility. I threw away the "Auxiliary Warning Module" to which the sender should be connected a long long time ago. I'll check the resistance, if its a heating element there should be a lowish resitance, maybe like 10 ohms. Perhaps then I can gently heat it from outside, wave a flame at it, and see if it goes open circuit. In any event if I do want to use it again, with no Auxiliary Warning Module, I would need to design a circuit to power it correctly and illuminate a lamp when the circuite opens .... mmmm... probably leave that to a winter project.