Which zetec should be bought for zetec conversion and future turbo? I wanted a 1.8 and have read that the 1998 onwards 'black top' series 3 zetec is the better engine?

Are the series 2 zetecs worth buying?

Secondly, how much is a set of standard Focus RS pistons + rods in good condition? (incase i decide 2.0 zetec instead)

Or price to pay for equivalent 1.8 pistons + rods to suit a turbo?

Thanks, Aston.