I came accross the same question, You can do 1 of three things bud,
1.) Make sure the stock is legit, and save yourself the headach for now and just slap it on, make
some boost just to make sure everything is okay with the other million things that could go wrong before you get rid of your stock oil lines and plug water lines for an upgrade, and while your driving your stock mklll you put togeather i nice drop in turbo set up. manifold, ex. wastegate, dump pipe, oil lines etc.
2.) bite the bullet and get it done, do the nice upgrade deal with the sh*t you gotta do to get it in.
Or 3, Got to ebay search in supra turbo's, a brand called cxr racing makes a huge turbo, a t67 instead of the 26. that bolts to your stock exaust dp and manifold AND oil lines. sh*t even your stock innercooler piping doesnt need to change. the even offer a new downpipe the oen but not cast and NOT 2 1/2 inches, like the factory. you can get both shipped for bout 600.
I did three and got a new garret t77 thats in my map range. the cxr turbo spools and sounds and looks great, bout 30% cooler then stock, and caries the cfm great at 13 psi before boost cut. lol.