What are you talking about? The "YF-12C" designation was not a combat aircraft. It was a fake designation slapped on a regular SR-71 that NASA used for flight testing in order to hide the secret origins of the program. There was never a real YF-12C.
You might be confusing the fake YF-12C with the real YF-12A. Both designs were derived from the original A-12 and look superficially similar but are internally quite different. There is no practical way to modify an SR-71 to carry and employ weapons. I mean it would be like trying to convert an F/A-18F into an F/A-18G: not technically impossible but so complex and expensive as to be utterly pointless. If the SR-71 ever actually flies again it will be used for nothing more than aerodynamic tests.
> Ultimately, 935 became the workhorse of the program, with 146 flights between 11 December 1969 and 7 November 1979. The second YF-12A, 936, made 62 flights. It was lost in a non-fatal crash on 24 June 1971. It was replaced by the so-called YF-12C (SR-71A 61-7951, modified with YF-12A inlets and engines and a bogus tail number 06937).
You might be confusing the YF-12 with the A-12, which is related but a significantly different airframe.
I won't engage in discussing whether balloons are high priority or not. Let the 2023 events and the funding towards those areas speak for themselves.