So 18kg weight penalty. That's nothing. I'd take the iron block with a proper rebuild any day. If you were really worried could you just relocate the battery? All this talk of rebuilt xu10's makes me want to invest in mine for the 306.I did say from a "well rebuilt" engine. There's no issue fitting an XU10 into a 205. I have one in my race car. The weight difference is only 18Kg.