When I mounted my 90+ exhaust manifold, it seemed like the oil drain line from the turbocharger didn't quite line up with the hole in the block.  Other members of Turbobricks had also reported that they had had alignment and therfor oil leak problems.  Rather than relying on that seal in the bottom of the block, I went with a more closed system.  The 3/4" end of a 3/4" to 1/2" copper pipe union (solder style) fits right in that hole in the bottom of the block.  I epoxied one of these into the block with steel reinforced epoxy putty (good for 600 F).  I then cut the original drain pipe about one inch after the bend where the pipe starts to point to the hole in the block.  I then used about a 6" piece of Aeroquip "Socketless" blue hose to connect the old pipe to the nipple on the block.  Since this side of the oil system is not under any real pressure I just used good hose clamps to hold the hose onto the pipe and nipple. This system is almost 4 years old (as of Feb 2002) and I have had no problems with it.