Once a year we gather for a Thanksgiving feast with 3 or 4 turkeys cooked on a spit. Last year we rented a mobile unit ($$) so this year I came up with plans for our own. It can easily be sized up or down for your needs.
The BBQ was built as a dry-fit project - no mortar was used. It's a lot easier to assemble and, if the location doesn't work out, it's move-able. Also, if a brick happens to crack from the heat, it's easily replaceable.
NOTE: I won't really be addressing the details of the rotisserie motor. Suffice it to say you'll need an old electric motor (from a furnace or a clothes-dryer) with a gear-box that can slow down the RPMs. Ours is an antique unit that turns the spit at about 1 revolution per minute. I imagine a combination of bicycle gears could be rigged up to do the same thing.