Choose CMOS versions of the Z80 family chips: they usually have a "C" in the middle of the produc's code, i.e. Z84C006PEG for the Z80 CPU.

Also, choose 4MHz- or, better, 6MHz-compliant chips. You can see the different models by looking at the last number of the product's code, i.e. Z84C006PEG is 6MHz tolerant.

Choose chips of the 74HCTxx family. The "HCT" indicates a type of circuitry that is 74LS-compatible (the "LS" series was the original 74 family). The chips of the HCT series are compatible with the LS ones, because they have the same logic levels (despite the HC series, that don't). Since the LS series is difficult to find, I suggest to use chips of the HCT series.

Pay attention when you buy the video chip. The "A" letter at the far right of the name of the chip indicates a newer variant of the chip that Texas Instruments released to add support for bitmap graphics. The TMS9918 only supports graphics 1 (tiles) mode, text mode and muticolor mode, while TMS9918A adds the bitmap support, in graphics 2. 

These chips are almost identical. The former is the original one, developed by General Instrument, while the latter was developed under licence by Yamaha. They play almost the same, even though the Yamaha has double-resolution but double-rate volume envelope table, and someone says that the YM has different audio results. Basically, they are interchangable for our scopes.