Why not just buy the controller... It's only 85.00 from www.subaruparts.com
or from www.1stsubaruparts.com
for 80.75. They're not that hard to wire in. On most of them, I mounted them where they go in the rear area. On my legacy (1995 LSI Sedan) I mounted it where the cruise control computer is (Right behind the dash, mounted to the dash bar) and removed the cruise control.
Part Number: 22648AA011