Has there ever been a 7–3 in the Liga MX?

Yes, 7 times.

The first time: December 5, 1943, Guadalajara beat Atlas (Atlas 3–7 Guadalajara).

The last time: October 7, 1994, América beat Morelia (América 7–3 Morelia), 32 years ago.

Home wins: 4. Away wins: 3.

Nearby scores

1. 8–2 11 times
2. 8–3 1 time
3. 8–4 Never
4. 7–2 17 times
5. 7–3 7 times
6. 7–4 1 time
7. 6–2 60 times
8. 6–3 21 times
9. 6–4 17 times

All games

1. October 7, 1994 América 7–3 Morelia
2. April 9, 1972 León 3–7 Jalisco
3. December 15, 1963 Irapuato 7–3 Oro
4. April 1, 1951 Guadalajara 7–3 Veracruz
5. June 20, 1948 América 3–7 Marte
6. January 4, 1945 Marte 7–3 Asturias
7. December 5, 1943 Atlas 3–7 Guadalajara