i followed up this when i had my valver as i wanted to supercharge it..
look on vwvortex for some tips as theres loads of info on there.
wossner pistons and forged rods are the way to go.. you will also need some exhaust manifold made up, a common way (and cheap is the one from the audi S2 and chop off one of the exhaust ports and weld it up (as its a 5cyl). 1.8t inelt plenum mated to the bottom part of the 16v inlet is another thing they do but not essential.