It was operational until the late 1940s when it was taken out of service.
The Wellington Tramway Museum has given the Langs the job of conserving tram 17 while "minimising any likely threats to the fabric and heritage values of the tramcar" and "enabling the tramcar to be presented and interpreted in an authentic form that recognises its significance".
The aim is to have it operational at the Wellington Tramway Museum in Paekakariki.
Mr Lang said they are trying to keep the tram as true to its original form as possible, which means keeping the majority of the structural elements - save for some parts which are completely rotten.
"It will be operational so it needs to be sturdy," Mr Lang said.
Luckily the Wellington Tramway Museum has "bits and pieces" from similar trams that have now disintegrated - making the Langs' job slightly easier.
Making the job difficult is sourcing the equipment for everything apart from the running gear (trucks) for the car.
This includes electrical equipment such as motors, controllers, resistance banks and circuit breakers.
There are no seats and fittings and some doors are missing so the Langs will have to source these elements from trams and tram museums in other countries.
Mr Lang said another difficulty is that any knowledge of the tram structure is now largely gone so they need to be careful to document details of the tram's structure while taking it apart.
The Langs expect the job to take two years - 4500 hours of work.
Ali Lang agreed that the proposition was a tough one but "once you get into the work you can look back and say - I did that".