Quoted from Pafasa:
Hey Vid! I have Firepower and Black Knight. I want to rebuild the flippers (all 6) but want to get away from the coil spring. Does the early WPC flipper with the tab and rebuild kit work in my machines? What would you recommend before I buy parts?
One problem with BK you will run into is that the flipper on the upper playfield will have some clearance issues with the new longer/larger baseplate. But it can be done. I'll look around I remember someone doing a post about it, I have not converted mine yet but it is on my todo lis
Edit: Found it, I knew I bookmarked this. Siegecraft did an awesome job documenting the flipper upgrade to a Black Knight here http://www.siegecraft.us/blackknight6.htm
And seeing on a BK you will need the backplate, may as well just get an entire assembly instead of a rebuild kit. PBL has a good deal on a complete assembly for $36.50 http://www.pinballlife.com/index.php?p=product&id=172