The plan is to run the turbo remotely, from where the y connects to the cat. That just looks like the best location for it. What kind of oil pump will work best for the return line? Or would it be easier to fabricate a dry sump system, just for the turbo, using a pump to send the oil and then gravity for the return?
You're going to have a hell of a time making gravity pull things uphill. Remote mounts typically sit lower than the level of the return fitting for the oil pan. You will want to run a pump just to be sure. Even if the hose was level, relying on the oil pressure backing up in the turbo to push the oil back to the block is going to cause a leak in the bearings. It takes hardly any pressure to get oil leaking from the bearings. A manifold-mounted turbo has a vertical (or very near-vertical) return line so restriction isn't a problem - a remote mount isn't oriented in a way that will let this same concept work.
The engine provides perfectly sufficient incoming oil pressure for the turbo. You just need a pump to get it back to the engine after it's gone through the turbo. The easiest spot to tap oil from is usually the oil pressure sending unit.
My CarDomain page (link below) has some pictures of what my oil system looks like. The pump I'm using is actually an agricultural sprayer pump. It's been used time and time again on numerous turbo'd applications with great results. The only real concern with it is the incoming fluid temperature has to be reasonably low (less than 170F). I used steel line feeding oil to the turbo, then an oil cooler between the turbo oil outlet and the pump to get it as cool as possible. I haven't had a single problem with it so far. I wired it on a relay to the ignition (key on, pump on). I've also seen people use differential pumps as return pumps. Whatever works, the range is pretty broad.
The last thing you will want is a small sump tank below the turbo to let the oil drain out after the pump shuts off (when you shut the truck off). There will still be a little bit of oil in the feed line, and it needs a place to drain out of the turbo to keep from burning and caking up in the bearings. A half-quart capacity would be more than enough. I used a small chunk of channel steel with the ends welded shut as a tank. Looks clean, works great.
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but its still a pos ....
