The babbitt metal will destroy a caustic soda solution (ask me how I know this), and so will be removed before tanking the block, but if they have a non-caustic hot process, the cam bearings will be left in. BUT, they then should be measured for clearance, along with the cam journals, before reassembly. As for the heads, how old are the heads? If they're mid-'70s or older, I'm sure they could be milled to bring CR back up to where it was before. And Viton seals for the stems are great.