personally i say you need a diesel tank, lines, and pump so you dont run the risk of putting and gas into the diesel engine.
really you shoudn't under estimate a 6.9 idi i have seen them pull some pretty crazy loads and if taken care of last about near forever.
And the idea of the turbo on the 6.9 idi is not really a good idea even though the 6.9 idi and 7.3 idi do share some of the same specs they were non-turbo for a reason yes you can get an ATS sidewinder turbo kit or a Banks turbo kit, the kits are out there and i have seen them on those trucks but you run the risk of melt down because those engines were not designed for the forced induction.
And another note turning up the fuel on a 6.9 idi gives you smoke and a little more power but it also raises the EGT which pushes the idea of melt down yet again it can be done but a pyrometer gauge will need to be installed and watched closely
just my two cents worth