[time-nuts] Output impedance of MC74VHC logic?

[David C. Partridge]

Using this to buffer output from an LPRO (74VHC1G14 (Schmitt trigger 3.3V
TTL compatible)), or an Efratom 105243-003 10MHz OCXO with CMS output
(74VHC1GU04 CMOS levels) in a 10MHz mod for the KS-24019 RFTGm-II.

To match well to 50R bandpass I want to add a series resistor to the output
but don't know the output impedance of these single logic gates.

Does anyone know what this is please?