Take a Roco T-34/76 turret.
Cut off the gun barrel and replace it with the 57mm gun from a PSR 57mm / 76.2mm ATG kit.
File down the side angle a bit and then take the pistol ports from a Permit tank kit and glue them to the turret sides.
Cut off the cupola and replace it with a hatch made out of sheet styrene.
Take some plastic rod and make the ventilators for the rood; instant T-34/57.
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