Cheap turbo

The worst thing with running a turbo is all the little things add up quick , even with a cheaper turbo you will still need a good waste gate , a blow off valve all the hot and cold side tubing which really should be tig welded so you don't have to deal with slag ending up in your turbo, a good boost referenced ignition and fuel system boost referenced also with a carb built for boost so you wont lean out . Done right you would end up with quite a bit of money . I have always heard that whatever you think it will cost double that figure, and found that to be true.
Really if your goal is 400 hp , the cheapest way would be a stroker kit

http://www.hughesengines.com/TechArticles/10408416strokerdynotestingsept2002.php