Front "China wall" sealing issue on SBM

Mock it up. Install the gaskets and set the intake on and see how much of a void you have at the China walls and see if the corks will slide if. If so use them and apply a layer of Silicone to each side and blobs on the ends. If you have a small gap and they don't fit at all, re-silicone the wall to intake area and work hard not to get air voids in the silicone. Use a brand new fresh tube too.