Just for info, if anyone with a TEA is looking for a new distributor with or without electronic ignition installed, the unit in the attached link may be what you want. Cheaper than the Pertronix kit and includes a new distributor based on the Lucas distributor.
http://www.ebay.com/itm/Ferguson-Tractor-TEA-20-1947-56-Electronic-Distributor-/180706694056?pt=UK_CarsParts_Vehicles_CommercialVehicleParts_SM&hash=item2a12f553a8
Don't know if the company has one for the TO tractors, but they make them for many applications which can be found in their store.
http://www.ebay.com/itm/Ferguson-Tractor-TEA-20-1947-56-Electronic-Distributor-/180706694056?pt=UK_CarsParts_Vehicles_CommercialVehicleParts_SM&hash=item2a12f553a8
Don't know if the company has one for the TO tractors, but they make them for many applications which can be found in their store.