I wonder if there is enough room in the block to replace the crankshaft with a 3.55 mm increased stroke. That would bring the displacement to 2.5 liters. I know that would require a re-tune, but it would also increase the H.P. above 250 and further increase torque. I believe the factory induction components should still be sufficient to feed the added volume.
Then again, would a current production Subaru 2.5 liter crankshaft fit the bill. Or would our induction and and long block components fit on a 2.5 liter short block?