Replacing obsolete photodarlington with phototransistor
I made some corrections according to the picture you posted. 

There is nothing special about this phototransistor in the way is used here.

The higher current parameter ( up to 20 mA) is not used here since the bias resistor has a high value. 

Simply use a normal phototransistor like BPW76 instead with the original schematic. It is pin to pin compatible.