Block Hardware Package / Question

There is a difference between the old and the new one; the old one is deeper and fits better, but with the supplied gasket there´s no chance to seal (Gap is twice as thick as the gasket). I threw away the old gasket when stripping the block.....

maybe i try to get a rubber seal that´s thick enough, but i´m a little concerned about the heat from the block. Do you think it will last?

Michael