It looks close, I can't get at my pickup truck well enough to measure center to center, but I can measure outside to outside with relative accuracy.
Looks like I'm within 1/2" compared to the original 72 blazer rear I have sitting on the floor. Alot closer than the 78 blazer rearend I have.
Looks like you might be right Starvin.
Next time I have the pickup on the lift, I'll get a better measurement.