Farndon rods and Calibra Turbo (C20LET) pistons are a proven solution.. alternatively Ian Howell (as above) can sort you out a set of rods+pistons of whichever brand he has at the time for good money..

You'll need to run about 1.4 bar boost to get over 300bhp on a zetec.. with a t34.. then you have that pesky rs turbo exhaust manifold to battle with..