Fairly straight forward thought..
An original Focus Zetec motor has an 8 degree tilt towards dipstick in the engine bay.

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Mine is now mounted level 0 degrees in the kittycar..

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Is it fair to assume my low level dipstick mark now becomes my high level mark

Don't think it matters really but just one of those locost thoughts ...

If you're using a different sump it's normally altered to be flat not tilted so I think you just read the dipstick as normal.

I have always just filled mine to the normal level on the dipstick the oil level in relation to the crank will remain the same although the sump holds less.

Paul.