Stuck drums. More than one wheel cylinder on each wheel. Shoes worn down to the metal. Any part you thought you needed will be wrong. Some stuff may be made from unabttainium. The bigger stuff is almost always more time consuming. I hope I’m wrong and all goes according to plan. BTW, I had a early 70’s school bus in the late 80’s and everything I touched turned out to be a big ordeal.ðŸ›