Engine numbers

Hi all!
I have a 1962 TV175 S3, which has an engine number around 6000 units lower than the frame. I was given to understand that, until the '64/'65 models, these were around 3000 units apart. This is a lovely early (2015) restoration, so I just wondered if this could be the original engine, or did someone source one as close to the manufacture date as possible. Not an issue, but I'm interested if my information on 3000 separation is correct.
I have a 1962 TV175 S3, which has an engine number around 6000 units lower than the frame. I was given to understand that, until the '64/'65 models, these were around 3000 units apart. This is a lovely early (2015) restoration, so I just wondered if this could be the original engine, or did someone source one as close to the manufacture date as possible. Not an issue, but I'm interested if my information on 3000 separation is correct.