Are there any alternatives for 74LS__ chips?
A more modern replacement for 74LS chips would be 74HCT chips. They have similar performance, the same I/O specs, but are implemented in CMOS instead of bipolar technology.

74HC chips are similar, except that they use CMOS I/O specs, which means that they are compatible with other CMOS (e.g., 4000-series) chips.

CMOS and TTL chips can talk to each other under most circumstances, but you need to pay a little more attention to the details.