The machine shop is finally getting around working on my engine, 21 months since I took it to him. He now says it needs a new block. He is looking for a new block, he says that any of the blocks from the 40s through the 70s will work. He has a contact in southern CA is getting it for him (the guy says flatheads from old welders etc will work). Is that true (all flat head blocks with the same displacement are the same)? Will the mounting holes for things like the oil filter, etc be the same on every block year. This is a bummer to me. I really wanted the old block to be used. It has a crack between cylinders that has been repaired, he also says it has porosity problems, whatever that means, one of the freeze plug holes is very badly corroded.