I've thought about an S65 V8 transplant too if my turbos were to eventually go. Quite some time ago, I also had my eye on an E60 M5 front cut with the S85 V10, gearbox and wiring for $12K! It was a steal but I couldn't justify spending that much when my car was running perfectly fine. I'm kicking myself for it now, even though my car still runs without any issues. The V10 is almost 50kg heavier, making an already front-weighted car worse... but I could live with it.
