'91 M5. I'd be nervous buying a 94/95 530 or 540, regardless of whether or not the block was replaced. I've heard all sorts of weird things about the M60 engine that make me want to shy away from it. The M5's engine -- I haven't heard anything bad about it at all. When it comes right down to it, the general maintenance on the M5 will be more than it would be on the 540. However, I'd be much more concerned about the 540's engine.