Does anyone know if parts from a ABU C3 will work on a BCX?
Most (level wind, etx.) will but not all. In particular the 6600 has faster gears than the C3, although I'll bet you could put the slower 6500 gears in the 6600.
Keta, I can't help you too much with the BCX but if you'll go to Mike's Reel repair and hunt down either Mike or Ken, I'll just about guarantee they'll have the answer for you.
http://www.mikesreelrepair.com/