<VV> Transmission differences?

[Cash Case]

Hi guys-
I pulled my motor this weekend and replaced the trans and diff.
I was having trouble getting one of the three the bolts back in that 
hold the trans to the front cross member.  I have a late model ('65 
Corsa).  Typically I have found in all lates I have ever worked on, that 
there are two 9/16" bolts on the passemgers side and one '5/8 bolt on 
the drivers side of the front trans cross member.  I finally looked 
really closely and the bolt hole where the 5/8" is supposed to be is not 
a 5/8" but a 9/16".  After finding a long 9/16"  it's all put back 
together.  I've not seen this before.  Was there a difference in the 
front mounting bolts at some point in production for the lates?
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