Oil feed/return in the wrong place
 

I recently picked up a Garrett T25 (from a Nissan CA18DET) to replace my shredded GReddy TD04. I clocked the compressor side, but that still leaves the oil feed and return (center section) in the wrong positions - feed on bottom/return on top. I removed the four bolts and the retaining ring on the turbine (not to be confused with the snap ring on the compressor)and tried to clock the center section, but it will not budge.

My question is, if I can tap & thread fittings into the housing, putting the feed on top and the return on the bottom, will that work or is there something internal to the housing that requires me to rotate the whole thing?

You need to rotate the CHRA (bearing housing) as well. If it's stuck then you need to unstick it with some serious pb blaster, heat, freezer, channel locks, w/e it takes without messing it up.
The oil feed distributes oil throughout the housing then the oil just drains out via gravity. So the oil feed sees oil pressure but the drain doesn't. Attempting to reverse these is not the right way to go about things.

once the 4 bolts and brackets are removed it will seperate and spin freely. gotta give it some love if it's old and rusted.

I suggest clamping the coldside down and giving it a few wacks with a mallet to the turbine housing.

That was the first step I took to clock the turbo, before turned the compressor (snail) housing alone. It was a frozen, rusty beeeyotch. I think that I will remove it from the car and try again this afternoon. I'll P-Blaster it, then clean it, torch it, whatever, but I am going to get that sumbich free.

One other question...I did start and idle the car with the T25 in place and it leaked oil out the turbine side and into the DP. Is this most likely caused by the return being on top (oil sitting in the turbo and not returning to the pan)?

If the oil cannot easily drain out then it will bypass through the seals. Though the seals could also just be bad, which means you might be looking at a rebuild. You can get your rebuild kit at gpopshop.com if you determine you need one.

I thought it interesting that it only leaked on the exhaust side.

it'll do that.

it's easier for the oil to push past a tiny c-ring on the turbine shaft as opposed to the coldside. There's technically not really seals on turbos.