Boxster purchase questions

[PeterKo]

I'm currently eyeing a 2004 Boxster 2.7L, priced at $30K AUD. The service history is mostly impressive, with one notable exception.

The current seller, who is the fourth owner and has only had the car for six months, mentioned that the engine has been replaced with a newer 987 model, equipped with a larger IMSB. This was apparently confirmed in 2020 by the technician who worked on the clutch and flywheel, stating it's indeed a later engine.

Interestingly, the owner mentioned that Porsche typically reuses the old engine number when replacing engines. However, during a thorough vehicle check, I found a note from 2011 indicating an IMS failure. The owner at that time commented in 2012 that Porsche declined to assist with this issue. They were contemplating an engine rebuild. Assuming the engine was indeed rebuilt or replaced, it would mean the current engine has only clocked about 40,000 Kms.

My queries are as follows:

1. Is it feasible to fit a 987 engine into a 986 model?
2. In the case of a 987 engine fitting, would they retain the original engine number? And if so, does this still pose an IMSB issue?
3. Should the engine number inconsistency be a major concern? I'm considering that if it was rebuilt, a Porsche IMS replacement might have been used. Would this be problematic in the future?
4. Any other questions and answers would be great in helping me make a decision.