A friend of mine keeps telling me that the new M5 is built on a totally different platform then the regular 5 series since they do the same thing with the M3/3series. Just doesn't seem to make any sense to me cause the car looks the same and all the body panels and stuff were interchangable with the previose M5/5series if I remember correctly. Could he be right?

I think you are right. I'm pretty sure they share the same platform.

Yeah, Im also pretty sure. Not with the M3/3series though right?

No, I checked out the BMW site, and it seems the measurements and stuff are the same for the 3/M3 so, Im guessing the platform is the same as well.