This is really the tip of the iceberg. If you've got a stock turbo and just want a simple and fairly cheap upgrade then change the compressor wheel to one off an 84-85 HA car. The compressor will go right in without modifying the compressor housing but you will need to balance the assembly. If you do a search for work turbochargers the owner is Reed Partridge and he can help you with further upgrades for the stock unit. If you want to go with the TTA compressor housing check evilbay. They come up every so often and are usually at a decent price, then get hold of Reed to help you do the mods you want.
If you go with a TTA housing then there's 1 more upgrade you can do but this is a max power effort. You will basically have a TE-62 DT (draw through) which flows close to three times what the stock turbo flows.
Again, this is a max power effort and you need to know all you can on tuning ect to keep from blowing the engine.
