Help needed with sb 318

I found a lot of gunk in a 273 that I was rebuilding. I took all the steel plugs out (2 were paper thin) and took a pressure washer nozzle into them and blew out the state of Rhode Island. The worst buildup were the plugs at the flywheel. They were packed solid. My drains did nothing when removed, took a screwdriver and had to displace some 50 year old sediment in there. You can do this with the pan attached but getting the rears out requires a pull. Use brass plugs or paint the backs of steel with RTV.