The problem is that while the turbo's are generic in design, there are such things as the AR ratio and other specifications that determine when the turbo peaks. Which is terms of the mass of air flow and RPM.
Then there is the flange problem. EVO TD04 and TD05 turbo chargers are the most common and then the T25. Some makers use a flange that is unique, like Subaru and Volvo. If you want to make your own header flanges are out there for fabrication. If the Turbo set up is for the same size engine and make swaps are pretty easy. But when you start mixing engine parts between different makers it becomes a night mare.
I know because I am adapting a Volvo turbo (TD05) to fit on a EVO manifold. It requires a lot of work besides just clocking the housings. It is just not as easy as it first seemed.
Check out http://www.miataturbo.net/, specify the section on DYI. I double check it a lot as I am not that smart by my self and it is cheaper to learn from others mistakes.