I too like the idea of discount MBT in WW2...fast, lots firepower and hot suspension. I guess you can just use hellcat or jackson for more knocking sniping.
That was actually the plan or doctrine of that time. The early Sherman with the short 75mm gun was intended to break trough enemy lines trough exploiting gabs and weak spots attacking the rear as a medium tank where as the M10 tank hunter and anti tank guns used by the infantry should eliminate enemy armor if necessary.
Well when Armored Corp did testing at Aberdeen, they shot at a target at 500 yards(iirc) after 20 or shot and zero hits they gave up.
Now sure the 76mm on a easy 8 looks scary. Hell look up the actual round it fired compared to the 75mm one. but when over 80% of the things you shoot at are infantry and light vehicles, you will probably want that bigger boom of the 75mm.
The british 17 pounder (76mm) had better armor penetration with it's APCR rounds compared to the HVAP rounds from the US sherman. But not by much. They did tests on captured Panther tanks in Isigny 1944 and had comparable results. However the 75mm is often seen as anti infantry weapon but it actually was an anti tank gun.
Well it is less of a anti-tank or anti-infantry gun and more of a all purpose gun that used a lot of different ammo types. That way of thinking is probably a hold over from the M3 Lee when the turreted 37mm was the anti tank gun and the 75mm was considered for bunker busting.