I have a 71 challenger convertible 340 optioned as an R/T. Manual breaks and steering. I'm trying to replace the front break shoes but I'm having a problem with the size, I looked on rockauto and called local auto parts store, they show a 10 1/2 x 2 1/2, and an 11 x 2 1/2 also an 11 x 3. However my break shoes measure 12 1/2 x 3. I don't know if someone used the wrong breaks in the past or there is some special configuration. Any info would be appreciated

 

What do the drums Measure?

 

As close as I can measure drums are 3.25 x 34

 

Are we doing MM's or INCH's?
What dose the drum say on it?