All you need is a spacer plate for 8.5 compression and you are easily safe for 400hp. Rotrex chargers are £1200 for a kit of just parts Second hand eaton M90 off a merc should support your power goals in the 300bhp range If you can find the space eaton m112 off a XKR is good for around 500bhp. Will be cheaper to wait for second hand kit but if your after a project go ahead with DIY,