Hi, I found the very first schematic of this amplifier, please note that the pcb has some different componets, wich is highly optimised to work with lower impedances. Although i not recomend using this amplifier on bridge, because of the high currents that returns to the transistors. It can easily done by using a pre stage with opamps with inverted phases one against the other, and put two boards in bridge.
Use this only on 8Ohms for subwoofers, but from my past testing experience of this amplifier, in bridge you will get a lot of distortions on mid high frequencies, and the circuit can oscilate easily on high inductive loads.
For higher output power you can use discrete amplifiers with the 2sc5200 and 2sa1943, it distorts less and can handle more power, Darlingtons are great when no more than 400w/ch are needed.
Be sure to check the ɥFe of all the darlingtons you have and chose the ones that have the same values, or almost the same to ensure the stability of the circuit.
Best Regards;
Lira