Lets talk about distribution blocks!

[Ackattack]

So I'll be running disc brakes on all 4 corners and need a distribution block. I have a few floating around. One is from a 72 3/4ton (so front discs, rear drums). The other one is from my 68 C10, but it had disc brakes on the front when I bought it. So I don't know if this one is a drum-drum or disc-drum distribution block.

I want a drum-drum distribution block. Are there any identifing marks on the blocks to be able to identify them?

Thanks