I am not a brake expert, but why don't you just remove the drums and look at the pads? Jack up the rear end and remove the tire, then making sure to block the tires release the parking break and remove the drum... I replaced my rear pads at about 35k because they were squeaking. It appeared to me that there was plenty of life in the pads. It is not too bad of a job, but I have done it many times on various vehicles. If you don't have the right tools it can be a bit of a knuckle buster. Be sure to make a diagram of all the springs etc... when you remove them...
Robin in Bremerton