Why not try contacting to gumtree seller of the gen3 angine & box I linked earlier to see if you can get into contact with the person who bought the engine?
I wouldn't worry about the Celica gearbox comment in the ad because when I spoke to the guy about buying it he didn't really know what he was talking about spec wise of the engine. Said it had twin wastegates and a big factory turbo :)
I'd say it was an MR2 box.

I have a 1MZ conversion at the moment. I've been told many times that the torque of the V6 is to much for the NA box. 

Appreciate the offer, but I just want something heavy duty that wont fail on me. I plan on tracking the car and enjoying the streets a little more than I should, so I think the reliability of the turbo box is something I'll need. I also plan on tuning the engine in the future, so it just makes sense for me to get the best option the first time round. I've contacted the guy with the gumtree add that was previously posted. I'm 99% likely going to buy that box. Just going to need LSD shafts, turbo hubs and turbo gear linkages next. 
Thanks guys :)

Hey Guys,
just an update on my situation. I have finally bought the gearbox I've been wanting with all the matching shafts, hubs and gearbox mounts. I've finished UNI for the year and finally have the time to do the conversion. The only problem being I'm still short just a few small parts. I still need the turbo model linkage cables, apparantly a new starter motor and a e153 speedo sensor. I've been told the speedo sensor and starter motor from my current gearbox wont work in the turbo box, can someone please confirm this for me?
Look forward to hearing back, thanks again.
 
Cayn. 

Hey Arty
 
Thanks for that bit of info. I think I will go with the turbo shifter cables, I've seen them for sale on here for $40 and I've also heard of people struggling to get into certain gears if they don't. Do you know if the starter motors are any different? I couldn't imagine they would be, but I've been told so. 
Also, if anyone if you or anyone else knows of anyone who is selling those parts can you please let me know.
Thanks for the quick response. 

Hey guys,
Just a quick update. I've ordered the speedo sensor and all the other parts required to swap it into my car from Road & Track. I've been told they have to order some parts from Japan or something of the sort. I sent them a deposit so they will go through and do so and haven't heard back from them since. Don't know what's going on there, honestly feel a little ignored. So, all i am waiting on now is for the part to be delivered and a set of turbo shifter cables. Again, if anyone has the part or knows of anyone who is selling this part please send them my way. It will be greatly appreciated. Once it all arrives I'm ripping into it. I am dying to see it drive. 
Thanks for the help so far. It has helped me a lot. 

Cayn.