Some time ago we discussed a problem with rebuilt YBlock distributors.  Cardone, the source of these rebuilds was using rebuilt small block Ford distributors and selling them as 1957 and up YBlock replacements.  The issue was the position of the drive gear in the small block distributor.  The distance from the mounting face at the base of the small block distributor body to the gear was not long enough causing the distributor gear to miss the load bearing surface in the block. 

A friend in our local car club asked me about this issue a few weeks ago.  I relayed the problem to him. This morning he showed me a Cardone rebuilt YBlock distributor he purchased within the last few days.  Upon inspection, I could see that the distributor gear had been relocated.  They redrilled the shaft and relocated the gear.  Enclosed in the box with the distributor was a diagram and instructions on measuring this critical distance.    It looks as if they may have fixed this problem.  My friend will be installing the distributor soon,  If he has any problems, I will report back.