180whp is possible, i am not sure that it will live long at that power level, they never seem to.
the key to make power is to keep the engine cool, use a good injection pump, and use a good turbo like he200wg or he221w. idi engines are not forgiving when it comes to heat.
i would recommend you use arp hardware in the bottom end and possibly use the tdi h beam rods, you will have to clearance your intermediate shaft for them to fit
the sdi cam is a bit hard to find, and a mild upgrade, the money is better spent on a dr diesel cam from giles, or a frank06 cam(assuming it will work with an aaz)
for the gearbox any watercooled 4 cylinder vw transission will bolt on. if you stick to an 020 it will bolt straight into your chassis.