TÜV for project vehicle?

Hey,

I was thinking about getting a project vehicle and was thinking about installing a different engine because I like to modify my vehicles and make various changes.

And my question now is: Would the car get TÜV (road approval) if I were to install, for example, an RB20DET instead of the original engine?

(I live in Bavaria)

because it has a different exhaust system that you probably have to make yourself depending on what kind of vehicle it is.

I'm not entirely sure if this is allowed, so I wanted to ask if anyone knows anything about it.

Thanks in advance!