Quote: The HP and some other big cars were supposed to get the 8-3/4 through the early part of 74. The later part of 74 they dropped the 8-3/4 for the 9-1/4.
The light duty B bodies were supposed to get the 8-1/4.
You sir, are CORRECT! The 8 3/4 went away in 74 (at some point) and the 9 1/4" replaced it. I have the 73/4 parts manual around here somewhere...If I can find the changeover date, I'll post it back.
This is also true of Dodge trucks.
I am, however, curious as to what rear a late build 74 360 4spd Cuda/Challenger would have had.... I've never seen a 9 1/4" E-body rear.
I've never seen a 9 1/4" E-body rear. 
