Nic,
Here's the original spec list from 1994 as the bike was originally spec'ed and sold. 8 Speed Dura Ace STI. If your taking it back to original spec I'd buy someone else's complete bike to get the Shimano parts and then sell off the rest. That's going to be the least expensive way to get the DA parts.
Sorry to hi-jack slightly but thanks for the BikePedia link, very useful. I've now managed to date my Giant TCR as a '97 model, more Retro than I thought!