Need Help identifying my Rear Axle

[Ziptang]

Restoring my 1974 Roadrunner.
originally a 318 with Auto tranny.

I'm putting in a 440-485hp. Engine and Tranny are fitted and ready to go.

Need to address the rear. However, I'm having trouble indentifying the rear axle. I'd guess a 8 1/4" but I'm not sure.

See pictures below.

 

[dryheat]

It is a 8.25 ...

 

[tpodwdog]

Looks like 8-1/4 to me!

 

[Ziptang]

Thanks.
Now to find a replacement..........