When there are shafts involved in the equation, that gasket thickness is figured in clearance and alignment at the factory. So usually using something out of a tube isn't the best fit. You can patch a gasket with it or make up for a bad cut if you decide to make a gasket. Usually using it alone is less than satisfactory and in most cases when you are not talking about end gaskets on a chevy small block's intake manifold, a GIANT step backwards when a gasket or oring was in the original design. Why butcher it when you went so far as to get another case to begin with?