1968 Radio and Speakers question

I have a stock 68 Xr7 factory radio and speaker. I wish to replace the speaker and update the radio at a later date. Is the radio 4 or 8 ohms? If I use this speaker, will it work with an updated radio?

Dash Speaker - 4 Ohm Tri-Axial - Repro ~ 1967 - 1968 Mercury Cougar / 1967 - 1968 Ford Mustang ( 1967 Mercury Cougar, 1968 Mercury Cougar, 1967 Ford Mustang, 1968 Ford Mustang ) at West Coast Classic Cougar :: The Definitive 1967 - 1973 Mercury Cougar Parts Source

Old radios, including that one, are 8 ohms. 4 ohm speakers short the unit out. Use an 8 ohm speaker and you won’t have any problems.