This is an excellent reproduction of the manual you need! It covers installation, operation and includes a parts diagram with part numbers.
Ammco 7900 HD Twin Disc Cutter Tool Operating Manual
Ammco 9249 Tool Holder Set Screw Kit for Twin Disc Cutter 4000, 4100 Brake Lathe
Ammco 906905 Twin Cutter Head Springs for 6900 & 6950 Brake Lathe Cutting Tool
Ammco 6900 Twin Cutting Head for Brake Lathe Cutter
Ammco 4000 4100 disc Brake Lathe Rotor Feed Gear Box assembly 7751 b 798
GM Dealer Equipment Ammco 4000 GM Disc & Drum Brake Lathe Manual