I know its not the same thing…. at my restaurant I use a top round for our roast beef, with the fat cap trimmed off. We cook ours in a cook-hold oven. I use 17 minutes per pound for a cook time, at 200 deg. After that, hold in the oven at 140 deg. for at least 4 hours. The oven is programmable so I in put these times and temps. When the roast is finished after the appropriate cook and hold times, it is around 135 deg. It is not fall apart tender… but this may help with your times and temps in the smoker.
For catering events I do at times slice our cold roast beef in to a full size restaurant pan shingle style, then partially cover with beef stock, cover the pan with film wrap and foil and reheat. This is almost fall apart tender at this point.