Just spoke to rocketralley. Their spool will not fit the STI 6 speed transmission, only the Legacy Spec B 6 speed. But, they suggested that an easy solution would be to just weld together the two shafts. Any potential problems down the road for me if I were to weld these two shafts together to convert my trans to 2WD?
Also contacted a local PPG vendor to see if their RWD conversion spool will work on my 07 STI transmission, and if so at what price. SpeedForSale said it would take a day or so to confirm since PPG is in Australia.