Are you simulating or laying out a board. For layout, just substitute a 74HC part with the same footprint. For simulation, a digital sim should work out about the same as HCT but simulating the analog behavoiur of a pin attached to a net it might be different.
If you are not simulating but want the components to have the correct part numbers, I usually create new components by placing existing simialr device (say the 74HC00_6v) on the design then editing the component in the database, I change the name and delete the model then save in the user library. It's faster than creating a new component from scratch using the wizard.
