I have been working on a 300zx...the line that is in question is the one that threads into the top of the turbo it curls around twice and bolts onto the turbo as well as threads into the turbo as well. it bolts into the side directly opposite from the drain into the block.

Problem is, the factory turbo line is too small to thread into the turbo. it is the exact same size as the side that threads into the block. I cannot find the part at any auto parts stores. I believe it is a 12mm fine thread bolt pattern. i can post pictures and into tomorrow. I just wanted to know if anyone else has had this problem, and how they solved it...and yes, i used the search feature. on multiple sites.

 

You can try to find aftermarket flex oil feed line or order custom made flex oil feed line.
Nissan 300ZX Performance Turbo Parts, Upgrades, and Accessories