67 cuda FB progress UPDATE

Ok, so as you all know, I got the belly of the fish all cleaned up and lookin good but am in a holding pattern for a while because it'smy brother's shop and he is working on a few cars for a good friend of his and there is no room at the inn. a.k.a the paint booth / body work area.
I began cleaning up the 8 3/4 rear and have some questions for the people that know this sort if thing. Looking at the pictures, can anyone tell me ANYTHING about this Diff. by the numbers? I think I know what the big X means, but besides that I have no idea. I most likely will need to open it up to be able to tell the gearing as there is no tag on it indicating that it has ever been worked on or gears swapped out.
Anyways, lots of cleaning, wire wheeling and at this point I don't know why I haven't just taken it apart and sand blasted everything, seing as it all needs to come apart anyways because I am putting new wheel barrings on it and re-doing the brakes.

One more question. Why are the drums so difficult to find new replacements for this thing? they are 10 inch and have 1 1/2 inch wide brake pad surface. Summit showes they have only one and it's price is $78.00. WOW!

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