Hi mate,
I was looking into this myself when I joined the forum and decided it wasnt worth it...I am now going for a valver conversion purely for the reliablity issues. I have hard too many horror stories about the engines bursting into flames and melting pistons. Putting all your hard work and money down the toilet.
Also you have to consider little annoying things like the electronic speedo, the choke, the carb etc..
If you have a good engine and a mechanic that has done it before no problems, but for less money and more bhp as standard you could get an engine which is much more reliable. If you are doing it purely for the noise of the turbo spooling up then the dump valve releasing pressure, go for something like the renault 21 turbo engine (200bhp as standard) and much more reliable.
There is a guy on here called winston who is breaking loads of renaults at the moment...speak to him, he helped me out alot.