58 300 D generator question

[mjraguse@xxxx]

Could a few members with 300 D's please answer a generator question for me. 
The correct generator for non-air is the GJC-7013B. I have a GJC-7012-A 
which is a 57 Plymouth generator and is only 6 3/4" between the mounting 
ears. The mounting bracket requires 7 1/4" which is correct for the GHM 
series. 

Would you please measure the distance between the ears on your GJC 
generator. Could there be two different mounting brackets? Also the 
diameter of the GHM is 5" whereas the GJC is 4.45". If you haven't guessed I 
am trying to build a correct 58 generator but the differences between the 
7012 and 7013 seem to be more than the specifications indicate. 
Thank you to those who help.

Marv