That is a chain drive case and I don't think it will install on the W56. Is the C a forward shift case or what? If I were you I would scrounge around wrecking yards for the gear drive 4 cyl case that belongs on the W56. Maybe someone would even give you little trade in on your chain drive case... I wouldn't stress about cutting up the floor. You can make a nice plate to screw down and it will finish out just fine.
