There was a very rough rule of thumb in the steam era: top safe speed for a locomotive in m.p.h. = diameter of its driving wheels in inches.
(Very rough. At the high end, well-designed late passenger engines could exceed this by a wide margin: Milwaukee Road's 84" drivered Atlantics and Hudsons were regularly operated at well over 100 mph, and there are apparently reliable reports of runs on which their speedometer needles were hard against the 120 mph peg. And I think many low-drivered freight types were ... uncomfortable ... to ride on before they reached wheel-diameter speed.)
I think the highest RECORDED speed for a K4s Pacific was just under 100 mph, for a rebuilt and modernized (with poppet valves) engine on a test train in the late 1930s: a fairly heavy train, so a bit higher with a short train would doubtless have been possible.
H6 Consolidations were built for freight service, later used largely as switchers: I doubt they got anywhere near wheel-diameter speed on any regular basis. (PRR officially deemed its I1sa Decapod, with 62" drivers, good for 50 m.p.h.; they seem to be universally universally described as "rough riding".)
E3/E7 Atlantics were built for fast passenger trains, and later in their careers would have been used mostly with comparatively light trains. At a guess they would have hit 80 m.p.h. regularly in main-line service early in their careers.