Part of the problem is that a Chuck is a huge hunk of meat that can weigh close to 30 lbs. In this large mass are different muscles that do different amounts of work, and therefore take different amounts of time to get tender. Any part of this mass can be cut off and sold as "chuck roast". If you get one of the parts that is the toughest, then its gonna be a more difficult cook.
How does one look at a 3-4 lb chuck roast and tell if its from a more tender part of the chuck? Well I don't know because I haven't cooked enough. Maybe someone who would will chime in.
If I were cooking a chuck tomorrow and I wanted guaranteed results, I would season the roast, sear it all over using direct heat. Then I would put it in a foil pan that it barely fits into and smoke it until it is fall apart tender,, all the while cooking in its own fat and juice. Will this be the exact results you are seeking? Maybe. Maybe not. Will it be delicious? Almost impossible for it not to be