They are different tanks. The Tamiya kit is basically a final variant of the M4A1 (76) VVSS and could easily be used in a late WW2 setting.
The M-51 Isherman is the same M4A1 hull but has a different engine and engine deck, HVSS (Easy 8) suspension, a 105mm gun and a highly modified turret to accommodate the larger gun and plenty of IDF-specific fittings.