69 gt350 rearend vent

[J_Speegle]

Can't figure out on commonality on all of this other than the shock. Why should a BB auto with the same rear and shock arrangement as a SB car have a moved vent hole?

Not sure if "moved" is the way to look at it. It's wasn't moved as many prior years had the single hole, its just different because some engineer or group of engineers decide that was how they should be made. Plenty of 9" 69 rearend housings made for other applications that year with single holes. Believe the majority were. Lots of trucks and other big cars