There are two different setups for the Y-Block camshaft retention. The ’54 and into mid ’56 used two spacers and a fuel pump counterbalance and from ’57 on, it was a combination of three different spacers without the fuel pump counterbalance.  The fuel pump counterbalance is keyed and goes between the gear and the fuel pump lobe.  The later model engines simply had a keyed spacer that went between the gear and the fuel pump lobe.  It’s important that the various spacers go in the correct positions.  Here are some past threads that may help.

http://forums.y-blocksforever.com/FindPost65119.aspx 

http://forums.y-blocksforever.com/FindPost24561.aspx 

http://forums.y-blocksforever.com/FindPost53260.aspx