It wasn't A-7X but A-7F and it did not happened before 1985, as an USAF project.
Now, nothing prevented the USN indeed, putting the very Phantom F-4K engine (a reheated Spey) into an A-7E and create their own, NAVAL A-7F in 1965, 1970, 1975 or 1980.
Consider the fact that plain old A-7E still had 10% more range than freakkin' Hornet... plus the A-7F performance was truly awesome.
But the A-7 was always an ugly duck for both USAF and USN.
Clearly the low-end to the F-14 was not supposed to be the Hornet.
Could have been instead
- upgraded supersonic A-7
- Convair 201 / 218 VFAX (instead of NACF)
- Tomcat without AWG-9 and Phoenix, for ground attack