Where can I get seal plugs for drum backing plate? Plus wheel cylinder question

[70pumpkin]

Not exactly sure what they're called but can't seem to find these anywhere... 

Also, drum wheel cylinders seem to come in various bore sizes.  Does anyone know if it was 13/16 or 15/16 for a 70 Challenger with front disc brakes?

[Katfish]

They came in the last kit I bought, H7250

[DeathProofCuda]

https://www.rockauto.com/en/moreinfo.php?pk=965159&cc=1231737&pt=1752&jsn=886

[moreparts]

I've gotten the plugs alone on ePay. 

[70pumpkin]

On the Dorman site, it says the HW7250 kit fits both 10 and 11 inch drums.  But the Roseville site calls out the Raybestos H7129 for 10-inch drums and the Dorman HW7250 for 11-inch drums.  I have 10-inch drums.  Which is the correct part, or will both work?

The picture for the HW7250 shows only 2 seal plugs and for the H7129 no plugs.  I need 2 for each backing plate - found a Raybestos brake kit H4094 that supposedly includes 4 seal plugs and it's only $5.

[Brads70]

This might help with your wheel cylinder size question? This is what I used when I had drums out back with no issues.
https://forum.e-bodies.org/wheels-tires-brakes-suspension-and-steering/12/rear-drum-brakes-locking-up-before-fronts-try-truck-rear-wheel-cylinders/3018/msg43894#msg43894

[70pumpkin]

I was getting conflicting info from the Dorman site and the Roseville site. 

Roseville explicitly says the 7129 brake kit is for 10-inch drums and the 7250 kit is for 11-inch drums.  Roseville is correct.

When you search for a 1970 Challenger, the Dorman site says 7250 kitis the right part but that's not right -- if you look at the application chart, it's all for 11-inch drums.  I confirmed this with Dorman tech support.