what piston you use will depend entirely on what CR you want to achieve and what head you are using.

cheapest way out is to mill some off the top of the standard A12 piston. This is not a problem as long as you are sensible about how much you get lopped off. Besides, the skirts will crack long before the crown ever fails!

as for the inlet manifold side of things, you could simply run the inlet pipe from the turbo straight into the standard manifold - I've done it before...

if the budget is a bit bigger, think about a 3mm overbore and E15T pistons. They have a 19mm pin, so you will have to use late A12 rods or maybe A14 rods - it can be done.