Help ID this rear end

[MDPotter]

I bought this rear end on FB Marketplace and I'm pretty sure it's a 12 bolt, but I want to figure out a few details on it so I can rebuild and convert to 5 lug. I've been searching all over the forum and the internet and haven't been able to decode all of the codes. The seller thought it came out of a 70s squarebody.

Castings on the pumpkin:
-GM83
-3896839 N

Stamping on the axle tube:
-KAN
-300W91

Stampings on the ring gear:
-3819037
-9:37
-GM 2 801

Pics below.

My questions:
-Doesn't KAN mean it's a 3:55 open differential?
-Doesn't 9:37 mean it's a 4:11 gear set?
-Is there a way to tell what year and model (C10/K10/C20/K20) this rear end came out of? I want to buy the right brake parts, bearings, etc.
-What is the best deal on a set of 5-lug conversion axles?
-Can I use C10 5-lug drums off a 73-80 or do I need something different?

[MDPotter]

[mongocanfly]

You've got 4.11 gears..most likely the gears were swapped over the yrs..the axle orig came with 3.55s
The 300 means oct 27

[sweetk30]

and 12 bolt truck rear .

[Pontiac1976]

73-81 This most likely out of a k20-k25 since 6 Lugs.

Sorry tried fixing missed that it should have been C20-C25

[sweetk30]

Originally Posted by Pontiac1976

73-81 This most likely out of a k20-k25 since 6 Lugs.

6lug = half ton NOT 3/4 ton thats 8 lug .

[MDPotter]

I figured it was out of a K10 since C10's had 5 lug. So it looks like I can put C10 drums on? I see that there are two different shoe sizes on C10's and K10's but the corresponding drums appear to be the same, except for the lug pattern and bore.

And for axle shafts, will any 71-83 12 bolt 5 lug axle shaft work? It looks like the shafts for C10's and K10's are both 31-7/16" long and 30 spline.

[hatzie]

Look it up in the parts books...

KAN axle code was used twice on the squarebody trucks between 1974 & 1991.
8.75" locking rear with 3.08 gears from a 1974 K10
8.75" open rear with 3.07 gears from a 1979 C or K10 with JB5 brakes

8.75" is a twelve bolt axle.

It originally came with 3.07 or 3.08 gears. It's also 40 years old or older and gears are easy to change.

[MDPotter]

Originally Posted by hatzie

Look it up in the parts books...

KAN axle code was used twice on the squarebody trucks between 1974 & 1991.
8.75" locking rear with 3.08 gears from a 1974 K10
8.75" open rear with 3.07 gears from a 1979 C or K10 with JB5 brakes

8.75" is a twelve bolt axle.

It originally came with 3.07 or 3.08 gears. It's also 40 years old or older and gears are easy to change.

Thank you!

[hatzie]

The Ring gear stamping shows your present tooth counts... 9:37
I would say it's been changed out. 37÷9 = 4.1 so you have 4.10 gears in that axle not the original 3.07 or 3.08.

The production code stamping doesn't conform to what the parts books list so I can't give you a year of mfg or the plant. W could mean Warren Ohio but that W is in the wrong place in the sequence.