ABH versus AEC

Firstly, greatings from a new member.

I own a 100 S4 with a V8 engine ABH. Unfortunately, the engine is damaged, burning a lot of oil. Redoing the engine will be probably costly and I'm actually looking replacing it. I eventually found an AEC V8 (for A6, year 96) and I was wondering what would be the differences between an AEC and ABH. In fewer words, would it fit directly ?

Thanks for your advices.