The problem people run into with diesel turbos on gasoline engines is that diesel exhaust velocity is much lower than gasoline exhaust velocity. This is due to the difference in rpm operating range. The turbine housing from a diesel turbo are the limiting factor when transferring them onto a gasoline engine. Example, turbo ford guys running the 2.3l SVO engines will upgrade out of their stock turbos to run a turbo off of a 5.9l cummins. Which is why even a midly build 5.7l will flow to much to run stock turbos off of most diesels. The only differences between the latest "namebrand" hi-po turbo and diesel turbos tend to be in the turbine housing and impeller design, such that the turbos will function within the "efficiency islands."
Dual HX40(45) don't remember which, or HX55 would probably support your base build they are cummins turbos that come of some of the industrial equipment. But they can be found on different turbo oriented forums for fair prices.
