There were several diferent models of Shermans, weak, short 75mm gun or long, hi-velocity 76mm gun; generic-model, weak armor, Easy-Eight, better armor, or Jumbo, best armor (plus whatever troops in the field welded, piled or taped on).
I forget if the Firefly had the 76mm gun or some other, but it's said Michael Wittman (Tiger ace) would have pulled back, and not been killed, if he had known Firefly's were in the area.
Which model US tank-destroyer sported the 90mm gun, was that the Jackson?