I have compiled some Part numbers for Subaru 4 Pot Calipers with the 40mm Pistons (non Brembo)
Mine were off a 98 V5 STi but most of the part numbers should be the same for any of the earlier black coloured calipers.

1. Seal Kit - 26297FA050 Alt. 26297FA051
2. Bolt & Washer Assembly - 901130011
4. Shim Kit - 26298FE010
17. Piston - 26236FA010
12. Slide Pin - 26228FA000
7. Cross Spring - 26232FA020
8. Bleeder Screw - 26239FA000
****EDIT****
Now for what should be the matching 2 Pot WRX Rears

1. Bleeder Screw : 26238FE000
2. Cross Spring : 26632FE001
4. Bolt and Washer : 901120036
11. Seal Kit Rear : 26697FE000
14. Pad Pin : 26631FE000

















