For purposes of identifying chips:
A1 is a 20 pin DIP unmarked
B1 is a 14 pin DIP 74LS74
C1 is a 20 pin DIP unmarked
B2 is a 40 pin DIP unmarked
D3 is a 28 pin socketed DIP 2764 EPROM
A4 is a 20 pin DIP marked N32S153N, barely legible, may be wrong
B4 is a 14 pin DIP 7404