Is this an AMC 20 rear end?

I need to replace rear end bearings in my '66 Classic 770 232. I've pulled the axles out, going to get replacement kits for wheel cylinders and all the brakes too while I'm at it. But when I went to get the bearing kits, I keep coming across flanges which have 5 holes in them, where my diff only has 4 holes. Also a few youtube clips that I saw clearly show 5 holes on the diff housing, and mine only has 4. My diff is a 12 bolt which is why I assumed it was an AMC 20.

Or are there different types of AMC 20 rear ends and mine only has 4 holes on the axle housing but some later ones have 5, and all are interchangable?

Couple of pics below, if anyone could please tell me what type of diff this, or if you need me to take pics of it from another angle if there are any markings I need to be looking for? Any help would be appreciated. (p.s. yup ill definitely be replacing the diff cover seal too)

Hey thank you for that.

So just to confirm, as an example, here there are 5 bolt holes: https://www.amazon.com/Yukon-AK-M20-Bearing-Differential/dp/B0078U8LE2/ref=sr_1_1?ie=UTF8&qid=1529815779&sr=8-1&keywords=amc+20+bearing+kit

Does this mean the 5th bottom bolt hole just isn't connected to anything on my diff housing?