Well, one says this and the other thinks that, I think the least that engine manufacturers could do is to deliver a drawing with their engine sizes (for instance take a look at the zdz site). They all have internet sites do'nt they. for example CRRC pro is very mysterious
about their engine sizes.
When you have to measure the whole thing with a caliper you're in for errors, plus the drilling of the holes? more errors and all this together makes things not quite aligned at the end.