How to quickly identify 8 3/4 rear axle housing?

Today, I'm heading to look at an 8 3/4 axle housing for an A-Body with a friend. Are there specific features that can be identified to distinguish between an 8 1/4 vs 8 3/4? I believe the back of the center section between a 7 1/4 and an 8 3/4 are significantly different, but I'm not sure of differences between 8 1/4 and 8 3/4. Where is the part number located? On the shaft? Or on the outside area of the bowl where the center section attaches?

http://www.moparts.org/Tech/Archive/axle/6.html

Thank you for the quick response! Very helpful info!

Is it under the car or out? Make sure it's the proper width for an a body. They are the most narrow and in high demand, so they bring a premium. I don't know the width off the top of my head. Does it have drums and backing plates? They are unique for an a body. How about the third member? Look on the drivers side casting numbers. Look at the last three numbers. It will most likely be a 741 in an a body. That it the least desirable because it has the smallest pinion. It could be a 742 or a 489. See if it turns freely. If it does, have a buddy hold one axle with a bar between the studs and you try and turn the other. If you can turn it, then it's not a sure grip. I looked at one just a month ago and was told it was a sure grip. Performed the test and they both turned. He was asking 350 for a 69 Super bee rear that he thought was a sure grip. No sale for me that day. Good luck. Stay warm today!

There is no center section... just housing. The housing is out of the vehicle. I'm pretty sure my friend stated it had axle shafts with backing plates and drums.

Thank you once again for the feedback!

Housing only should measure ~52 5/8" flange to flange

Axles and brakes should be 4" bolt circle.

The center to center on the spring perches should be 43" for an A body housing, and it would've only come with small bolt pattern axles, unless changed out for aftermarket! Don't be fooled by the 65-67 B body housing, which is only an inch wider than the A body unit, but has large bolt axles! Also, the brake line distribution block on a 1969 and earlier A Body axle will be up on the center hump a little, whereas the 1970 and later unit will have the block down on the drivers side axle tube a bit! This may cause a problem with the length of the rubber hose needed!

There are two different A-Body housings too. The brake "T" on the housing moved after 1970 so brake lines will be different, just for future reference. The best way is to bring a tape measure and use the measurements listed above especially if it is just a housing. The early B-Body housing is 1" different in the frame rail spacing. There was never a big bolt A-Body 8-3/4, but plenty of people change brakes and axles.

Should be pretty easy to tell an 8 3/4 from a 8.25 or a 7.25 , the 8 3/4 doesn't have a bolt on cover on the rear ...

As far as telling one from the other ... tape measure ...