Yes there are black pullies that have the same (or similar) diameter as the Blue BBK pulley (M62). The M45 standard zetec kit came with a 3" pulley and the bbk pulley was 2.5". The SVT m62 kit came with a 3.6" pulley and the BBK pulley was 3.1".
I'm guessing that you have a M45 kit and bought the BBK pulley for a M62.
a 3" pulley would need a 104.5" belt. if you did have the 2.5" bbk m45 pulley it would use a 103.5" belt.
the 99" belt would be correct for the old style alt bracket and an m45 bbk however.
The 5.7" OD crank pulley should be fine with the standard blower pulley, but it wont be as good as the blower pulley as it overdrives all of your belt driven accessories (more parasitic loss) rather then just the blower.