Item 1. Everyone I've seen with 33's and a TT/shackle lift runs a 285/75-16, which is narrower but about 33" tall. With the right backspace on the rims a 33x12.50-15 might fit with some front trimming but I'd doubt it. Get a 15x8 with 3.75" backspace. (A 32x11.50 should fit fine with that.) Most likely you'll need a bodylift as well.
Item 2. Thorbirds are really a lousy tire under all circumstances except when covered with Armor All at a show. Wear fast, hard if not impossible to balance, and downright dangerous in the rain.
Item 3. For safety reasons, any tire from Interco should be kept to a maximum speed of 15 mph with the possible exception of Swamper SSR's.