I would say hold off until you plan out your turbo system. Its not that big of a deal to tap a fitting into the pan (or even remove the pan to install a fitting). As Hank said above you want to have that return in the right place to allow proper drainage of the turbo without restriction of any kind. As for the fitting, most systems just "dump" into the pan without regard for smooth flow of the oil or windage of anykind. However every bit helps, if you could extend the fitting into the pan (taking care to leave clearance for the crank and rods etc..) with a slight downward slope or maybe even a nice radius to drop the oil toward the rear of the engine then that would likely be perfered over just "dumping" it in the pan.
