That engine is built by AMG, so you are talking cams crank and possibly/ probably some head work. But be warned if you go to far down that road you WILL need to spend more money on gearbox, that engine will be capable of nearly 700# natural. There are only a few know tho survive that Ricardo (16k), porsche g50 and g60 (15-18k), Cima 25-30k....., there is also the odd lambo box that shows up from time to time
I guess you kinda get the picture, you could end up with 40-50k in drivetrain alone.