Steve Neeley has a list of objective to eyepiece specs for various makers at this page:http://user.xmission.com/~psneeley/Pers ... pieces.htm
For the old Leitz objectives, the distance from objective flange to first image in eyepiece was 152mm
For the old 160mm AO/Spencer objectives it was 148.7mm
So the actual difference was only a little over 3mm.
However the old 10X Periplan eyepiece that came with the Leitz microscope may have had different corrections than the Cat. 146 eyepieces used with the 4 series. Also, there is the matter of the 4 series having a tube lens just above the objectives. Still, I couldn't see any obvious differences in the performance of the objectives between the two stands, except the AO eyepieces have a much wider field, and the old Leitz objectives may not have been designed to cover a wider field.