Not an EE but I'll proffer an opinion. Pulling chips from scrap is largely useless because there aren't any datasheets available to identify the function, pino

Not an EE but I'll proffer an opinion. Pulling chips from scrap is largely useless because there aren't any datasheets available to identify the function, pinout, and timings to operate them. Options that come to mind are: Diode logic with an amplifier between each stage (https://en.wikipedia.org/wiki/Diode_logic https://en.wikipedia.org/wiki/Diode_logic) or DTL. Discrete surface mount diodes are still present on circuit boards and can be extracted for re-use. See the IBM 1401 for an example of a simple DTL computer. Relay logic (https://en.wikichip.org/wiki/relay_computer https://en.wikichip.org/wiki/relay_computer). Building relays by hand using scrap material is practical, though difficult. Expect your gizmo to have the size, capability, and power requirements similar to the Zuse Z2 ( https://en.wikipedia.org/wiki/Z2_(computer) https://en.wikipedia.org/wiki/Z2_(computer) ).