RE: Old Radio
The old Futaba systems with the 'G' connectors only used two leads on the battery pack, but had the 3-pin connector.
As far as the transmitter is concerned, it would not be legal to use in the current RC environment. Very likely, it's not even on a legal channel. Unfortunately it is not possible to get the transmitter converted to the narrow-band specifications. Even if it were, by the time you paid (anyone!) to convert it and purchased a new narrow-band receiver (you cannot convert a wide-band receiver to narrow-band), the costs would equal or exceed the purchase price of a new 4 or 6-channel basic system that would comply with the narrow-band specifications.
All wide-band R/C equipment became illegal to use in 1998. The Futaba 4L transmitter went out of production in 1986.