[sjf911]

There are a couple of significant issues that swapping out for a 930 motor solves. One is the turbo oil scavenge setup. The 930 motor has a mechanical scavenge pump driven off of the front of the left camshaft. This is difficult to reproduce on a stock 3.0 and might optimally require swapping out to a 930 or sportamatic oil tank for the scavenge connections.
Second is the engine oil scavenge itself. The 930 has a much better oil pump. A lot of people including myself return the turbo oil to the engine scavenge side (sump) probably exacerbating the already marginal scavenge capacity of the 3.0 oil pump.
This makes one argument for the GT35R because of greatly reduced oil throughput in that turbo.