If your housing and block surfaces are uneven, you can STILL get a leakproof seal the way I did .....

I glued the gasket on the housing, letting it dry overnight. Then instead of using bolts, I used studs with the same thread pattern. I applied gasket sealer to both the housing/gasket side and the block side. The studs helped it line up perfectly without slipping around and getting the gasket crooked like when you are trying to put bolts in. I cinched down the nuts and the thing never leaked again.