So while I search for used differential to replace the whiney one, I decided to continue the clean-up and refresh starting with the engine bay.  First thing, I popped off the dingy valve cover to replace it with one with a little more bling.  Wait a minute, why does this car (1975), have a single row timing chain?  Come to find out that the engine has been replaced with a factory rebuilt unit identified by Steve (Conserv) as a 1974/75 model, #0054, remanufactured in April of 1979, 1989, or 1999.  The valve train was very tidy and the cam lobes were perfect.  After buttoning up the new valve cover, I spent some time cleaning and polishing and installed a new set of factory stickers, including my own 1975 emission sticker.

Now that the original matching numbers restoration is off the table, I may look at replacing the whole intake side with Lynx/45 DCOE to bling it up a bit.

Thanks,

Mark92131