[Adam]

A 911 engine can be swapped in and that's what most people do that swap. The 911 engine is essentially the same engine as the boxster just bigger internally , meaning just a bigger bore or longer stroke or both. Externally they are the same size so swapping one in isn't a space issue. As long as you keep the ECM or engine computer consistent then the swap is pretty straight forward. The boxster and 911 went through a few ECM changes and variocam changes over the years. A 3.6L engine has 320ish hp btw. Here is a quick breakdown on what boxster goes with what 911 engine in general, but you can make any combo work with the right ECM swap and enough $$$.

Bosch motronic 5.2 ECM 97-99 boxster = 1999 3.4 911 engine
Bosch Motronic 7.2 2000-2002 base boxster and S swap in 2000-2001 3.4L e-gas 911 engine
Bosch 7.8 motronic 2003- to present boxster base or S swap in either 3.6L or 3.8L engine.

This is a basic breakdown, and I'm no expert, but this is what I've learned on here.