F-4 Phantom:
1. Note that McDonnell put the F-4B Phantom went into production in March 1961 - and McDonnell merged with Douglas in April 1967... one month after production of the 649 F-4Bs ended.
2. It is important to state which variant you are speaking of.
The USN/USMC's F-4Bs were fitted for long-range detection and interception of mostly bombers - their AN/APQ-72 radar had a good detection range, but was optimized for medium-high altitude operation. They were upgraded to F-4N standard between 1972 and 1979.
The USN/USMC's 522 F-4Js, built from 1966-1972, were fitted to add improved low-altitude detection and interception of both bombers and fighters - their AN/AWG-10 fire control system with its AN/APG-59 pulse-doppler radar was an improvement for many purposes. They were upgraded to F-4S standard between 1977 and 1982.
The USAF's F-4s, delivered from 1963, had different radars and operational concept.
The USAF's 583 F-4Cs (customized F-4Bs with no gun), built from 1963-1966, had the AN/APQ-100 radar system, which had a ground-mapping function that resulted in a system less-optimized for range than the F-4B's. They served until 1989 in the ANG.
The USAF's 793 F-4Ds (improved F-4Cs), built from 1965-1968, had the AN/APQ-109, which had air-ground capability, but was otherwise similar to the -100. They served until 1992 in the ANG.
The F-4E, built from 1967-1979, had the AN/APQ-120 radar, which had a smaller antenna diameter than the USN/USMC Phantoms due to the installation of the M61 cannon under the nose - and they had a significantly shorter detection and interception range. I have conversed with a former USN F-4/F-14 pilot who did an exchange tour on USAF F-4Es, and he said that the F-4E would detect a bomber at the same range that an F-4B/J could detect a fighter. 1,387 were built for US and foreign users, and some are still in service (with
Iran,
Japan,
South Korea,
Greece, and
Turkey ), although much-upgraded.
Viggen:
The initial production version (AJ-37) was a "strike fighter", and was not even flying on 1 September 1970.
In April 1968, the Swedish government formally issued the authorization for manufacturing of the Viggen to proceed. On 23 February 1971, the first production aircraft, an AJ-37 model, conducted its first flight. In July 1971, the first production aircraft was delivered to the Swedish Air Force.
In June 1974, the first JA-37 (all-weather interceptor version) prototype conducted its maiden flight.
Mirage F.1:
Not even in production on 1 Sept. 1970.
Construction of the first 85 production standard Mirage F.1 were authorized "in late 1971", and actual production work began in October 1971.
During May 1973, the first deliveries of the production
Mirage F1C all-weather interceptor to the French Air Force took place; the type entered squadron service with EC 2/30
Normandie-Niemen in December of that year.
I'm not worried about other nations, the UK's best BVR interceptors were UK-modified F-4s (FG.1s & FGR.2s), and the Soviet/Chinese radars and missiles were lagging well behind the west's best.
So I'd say that the F-4B/J is my choice for a BVR interceptor on 1 Sept. 1970.