Could 1960s technology produce a supersonic VTOL aircraft?

Was the technology available in the 1960s to build a viable supersonic VTOL aircraft?

Yes, but it would need a more conventionally stable design than a modern fly-by-wire aircraft.

The failed projects of the 1960s do not prove that the basic technology was absent. Engineers were making the necessary breakthroughs and could have produced a viable aircraft. It would not resemble a modern deliberately unstable fly-by-wire fighter. Period control systems would instead require a more naturally stable layout, making the result possible but different from the solution designers would choose today.