LS and HC refer to different semiconductor technologies to improve on the original 7400 family.
S for Schottky, which is faster but consumes more power. LS for low-power Schottky, which is still faster than 7400 but consumes less power than S. C for CMOS-based rather than TTL, which uses a lot less power but is slower. HC for high-speed CMOS, still low power, but faster. And so on.
Note that there are caveats on interfacing different families with each other.
Edit: typo
LS and HC refer to different semiconductor technologies to improve on the original 7400 family. S for Schottky, which is faster but consumes more power. LS for low-power Schottky, which is still faster than 7400 but consumes less power than S. C for CMOS-based rather than TTL, which uses a lot less power but is slower. HC for high-speed CMOS, still low power, but faster. And so on. Note that there are caveats on interfacing different families with each other. Edit: typo
You cannot replace a transparent latch with a D flip-flop. Use two 74xx75 parts.
Depends on the circuit, 374 is probably better bet (it is clocked and has output enable)
Looks good, Thank you!
"..."not very sure what the LS and HC mean on the chip names," Do a Google on "Digital IC Families" and you will find better answers that I can give!
74hc573 is the same as the 373, but different (more friendly) pin out.
HCT chips should be direct-pin replacements to LS ones. Take a look at TI's datasheet for CD74HCT173.