Will a rear end from a 68 Polara fit?

I found a 8 3/4 rear end from a 68 Polara complete "Drum to Drum". I have a 73' Duster.
I'm not even sure what body a Polara is? I just know it's big.
I have read some people say that other years would fit, but they need to be shortened? Who does that and what does it cost?

Thanks!