Tim and Six have you on the right track, JR. I typically try to run at 175, using a charcoal snake with two briquettes on the bottom row, and one on the top. I run a dry pan, and I have a temp controller, so I get to cheat a little (but it makes the temp control easier for me!) I will usually use top round because CostCo frequently has that available. I cut it about 3/8" thick (I like it this way), and with the grain. Since the goal is to dry the meat to your desired doneness, I always try to blot as much marinade off the slices before putting them on the WSM as I can. Otherwise, it just takes a bit longer on the smoker, as there's more to evaporate.
Good luck!
Rich