My 7.25 is toast - where can I get a upgrade?

Hi, guys n gals.

I have a 73 Duster with a 74- 360/904 combo, but it still has the little 7.25 rear end in the car. The oil in the rear was full o shiny metal flake and it's super sloppy, so I need a replacement. I'd like to find a 8.25, preferably rebuilt and a direct replacement. I can't seem to find a source anywhere. I'm in Melbourne, FL (near Orlando) Thanks in advance for the info.

EDIT: I'm wanting to upgrade from stock as I'm hoping to get more power. I figure if I'm having to replace it, I should upgrade. I was mainly wondering if there was a known company that supplies them.