Just been all through this bollux myself so here goes.....There is only one type of Blacktop pump - the silver top has two types depending on the drive belt routing hence you can swop the 1.8 for the 2.0 type. The Silver top cambelt only has one idler / tensioner so allowing the pump impeller to sit directly over the hole in the block.... the Blacktop has two therefore the pump has to be offset to the right towards the exhaust. To obtain a short 1-2-3 point belt run requires a reverse pattern impeller to be fitted or get creative with various idlers!