hi,
i've just finished the most of my conversion, took me about 18 month and
a lot of thinking and re-thinking..and about 2500€ for spareparts (so far;))
i think the most important ist:
-Big intercooler + oilcooler
-TDI-tranny (mounted with G60 parts)
-Good pump, 10 or 11mm plunger
-Garrett T3 turbo
-new bearings etc.
Get the block bored & honed to fit oversize-pistons (smallest possible) and take a new head..
also think about bigger brakes.. the 256X13mm disks on my Audi are about to melt! (have 280x22 ready to be mounted soon)