I'd cook it on a Kettle. Coal on each side over a drip pan. It'll take about 1 1/2 - 2 hours may be a bit longer. I start mine at 450 and by the time it's done it'll be down to about 350. Krispy skin and done just right in my opinion. The WSM times will be all over the place depending on your temps, with or without water. With or without a water pan all together. My turkeys on the WSM would take 5+ hours at 270 ish with water but were pink in color, rubbery and smokey. My favorite part of turkey is crispy skin and I cannot achieve it in a WSM. Low and Slow will not be much of a benifit to turkey meat. It's already tender and It will get plenty of smoke in a short cook. Have fun.