Harken Magic Box (help!)
Most bb blocks have a little bit of space where it looks like an extra bearing could fit.
The most important thing in regards to the well being of your bb blocks is that they be clean. Rinse your blocks regularly for a long, happy working life. If dirt/grime build up, clean w/soap and water. Use only dry lubricants if you must(ie McLube) other stuff will work good at first but collect gunk.
One phone # is (262) 691-3320, they might be able to send some diagrams or something of that sort. If I remember correctly the line should dead end somewhere at the fixed part of the box, not really sure though. just look at it as a mainsheet system that you can''t see. Tape the line (3/16" or smaller) to a straightened coat hanger and feed it around until you don''t have any more sheaves to go around.......if you end up exiting where the becket is, you started at the wrong end(working end should exit at the bottom)