For a Mig-25PD Foxbat-E, an A-12 would have a "0" chance. They have been spanked out of Soviet airspace everytime they come into contact with an opposing Foxbat. A-12 wasn't even used in combat or overflew Russia.
First flying in 1962 A-12's initially flew with J75 engines (17,000 lbs. thrust each, much less than Foxbats), as the more powerful (31,500 and later 34,500 lbs. thrust) J58s were not yet available due to development problems. These J75-engined aircraft were only capable of approximately Mach 2.0. So had a J75 engined A-12 been flying today, it would be cannon fodder for an F/A-18 EF, which is a better dogfighter
Later the J75 engines were replaced with the J58's as the new engines became available, with the exception of the A-12 trainer "Titanium Goose," which retained the J75 powerplants for its entire service life.
All those engined with the Pratt & Whitney J58 engines were capable of only Mach 3.2. At this rate a Foxhound's AA-9 Amos with Mach 4+ speed would take down the SR-71. Blackbirds weren't ever made to track, lock on, shoot or destroy enemy fighters much like F-14s or F-15s, neither an SR-71 nor A-12 stands a chance against any current Foxbat or Foxhound made today. Every Blackbird driver would be completely aware of that little fact.
At Mach 3.3 the A-12's getting nowhere. Foxbat has the advantage in playing cat-N-mouse with the Blackbird. Its safer for the unarmed SR-71 to speed away at Mach 3.5 thats if its airframe doesn't rupture rather than an A-12 to dogfight at a max. of Mach 3.3, because it has no chance. The only way SR-71 could "intercept" a Mig-25 would be by trailing its path and crashing into it
