Assuming that one of those forty-pin devices must be the microprocessor ... well, the Intel 8088 (also 8080 and 8086) came in a forty-pin DIL package. And, looking at the image of the underside of the main board, once again it looks like U9 has the most connections ... so I'm going for that one as the microprocessor. It is also the one nearest to the EPROMS!
Other chips:-
HD74LS04P (U17, U19):- Hex Inverter (x4)
SN74LS32N (U23):- Quad 2-Input OR Gates
SN74LS153N (U11):- Dual 4-line to 1-line Data Selector/Multiplexer
SN74LS393N (U18):- Dual 4-bit Binary Counter
HN462732G (U1-U6):- 8-bit 32 KB EPROM
Already noted:-
74LS154 (U8):- "1-of-16" Decoder/Multiplexer
MM74HC32N (U14):- Quad 2-Input OR Gate
SN74LS374N (U15, U16, U21, U22):- x8 clocked flip-flops
