Calling All Eaton Rear End Guru's

[roger0080]

I need some info on the Eaton rear end brake drums from those who have them.
Trying to upgrade my brakes.

I am all confused when looking at the GM parts book and online parts sites (www.rockauto.com, www.federal-mogul.com (AKA wagner) etc) as to what would interchange on which axle and what is ACTUALLY on the axle.

From What I can tell (Eatons ONLY; not talking about Dana's):
67-72 C20 2WD Eatons have 11-5/32x2-1/2" shoes
67-70 K20 4WD Eatons have 12x2" shoes with 1/2" studs
71 C20 2WD Eatons have 11-5/32x2-1/2" shoes with 9/16" studs
71 K20 4WD Eatons have 12x2-1/2" shoes with 9/16 studs
72 C20 2WD Eatons have 11-5/32x2-1/2" shoes with 9/16" studs
72 K20 4WD Eatons have 11-5/32x2-1/2" shoes with 9/16" studs

Q: GM parts book lists the hubs as different between 67-70 & 71/72 so I suppose
that means 1/2" and 9/16" studs respectively in those years?

Q: According to the GM parts book, all 67-72 4WD 3/4Tons have the same backing plate. How does a 11-5/32" drum fit on a 12" backing plate?

Q: Whats the difference in the drums between a 71/72 C20 and a 72 K20 drum ?
Books say these are all 11-5/32" drums yet give 2 numbers for 71/72 C20 & 72 K20 drums and 2 different prices:
71/72 C20 drum $110.00 non-finned
72 K20 drum $55.00 finned;
waaaay cheaper! (www.rockauto.com); I thought the finned cools better (and would be more money)

Now here is my delema:
I have a 71 K20 Eaton with the oddball 12x2-1/2" drums, 9/16 studs (fronts are 9/16")
I have a 69/70 K20 Eaton with a NoSpin in it, but it has the 12x2" drums with 1/2" studs.

Here is what I am thinking to keep the 71 with 9/16 studs:
1. Take the 3rd member NoSpin out of the 69 and put in the 71 Eaton. No problem.
2. Get a set of backing plates off a 71 or 72 C20 and replace the 71 Eatons with these
3. Buy new C20 11-5/32x2-3/4" drums.
4. bolt it alltogther
5. Could I then use the 72 K20 finned drum instead?

If anyone outhere has these parts disassembled and lying around in their garage and sheds and could look and measure for me I would really appreciate or anyones knowledge of this.

-Roger
PS I don't at this time want to convert it to disc brakes; As long as I stay in the 71/72 years I should be able to swap around???
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