Lets start over how much money are you willing to spend on this car?
If your going turbo you better be ready to spend upwards of $5,000 on turbo parts and a built trans, that's saying that you buy all the turbo parts new and get a fresh rebuilt trans from TEP or ZZP or something.
Where as if you go with the top swap being as you have a gtp to take the parts off of all you need is time gaskets fluids and a tune. The top swap should not cost you more than $500 after everything is said and done.