How to select correct Tpd values to use from Datasheet?
The actual silicon in both 54HC00 and 74HC00 is the same. That's why they both have a maximum time of 18nS at 25C.

The 74HC00 (commercial grade) is only rated over the temperature range of -40 to +85, whereas the 54HC00 (military grade) covers -55 to +125. The 54 version will be slower over its temperature range.