Squarebody brake questions.

[Darkrider]

Starting a secondary thread concerning my current C10 project and a future one to figure out the parts needed for both trucks.

From the RPO code breakdown I got a long time ago for my '84 it has the JD5 brakes which from what I am reading is the 1.25 (1 1/4) front rotor with 2.75 (2 3/4) rear shoes. And further reading suggests the JD5 is simply a higher-weight capacity version of the JB5 which makes looking up parts a bit easier. Now my question is what is the core difference between the 1" (JB3 and lower) brakes and the JB5/JD5? The 1 1/4" rotor is obvious, but I'm assuming the calipers are different as well. I did the brakes on it last winter and had to grind down over half the pads to fit partly because I was sold the wrong pads. And partly because I suspect someone swapped on 1" rotor application calipers. Since I need to redo the brakes again this fall to do the job properly. Last time was a slap-it-together-and-get-it-running situation. Thus why I ground the pads down to make it work. I just want to be certain I am buying the correct parts this time. Are the pads the same between the two applications just different width calipers to make up the difference? Rockauto is giving no clear answers on this. Now to muddy the waters further.... I am in the process of buying a '73 C10 Custom Deluxe this summer and it too needs some front brake parts. However, when I look up parts for it on Rock Auto it doesn't even list a 2 3/4" rear shoe option. Did the early squarebodies only have the 1" front brakes?