So....The 74 series of chips started off with just that typenummer.
Later came LS versions which uses about 10x less power and should be compatible with the regular 74 chips BUT sometimes I still find non LS types on boards (like Galaxian). Sometimes these were swapped in later, and the documents say it should be LS, but some chips seem to be Non-LS on purpose, maybe for speed or maybe for fan-out properties.....
But.....non LS chips have been long out of production and hard to get. Is there a modern equivalent series that is 100% compatible with the original 74 range ?