I was playing around with the innards of model T ignition switch tumblers last weekend. Really a lot of fun. A friend of mine who teaches locksmithing at North Bennet Street School in Boston sent me an assortment of wafers. These are the small brass pieces that slide out of the way when the key is inserted. Turns out that the wafers for Datsun, Nisson and Subaru locks are a perfect fit once you file off a tang on the side. With a little fiddling you can re-key a tumbler for any number key.
Below: the model T wafer on the left ... Datsun on the right.
By the way, if you don't know about North Bennet Street School ... google it. One of the last great schools that teaches what are no considered obscure trades like piano tuning, violin making, furniture making, post and beam house building etc.
Mark thanks- this is good info...