I'd go vertical but cut it down to 42" to 48" and put a 3" pipe dead center in top for exhaust - probally 10" tall. 2 Doors with 3-4 removable cooking racks plus a difusser rack. Have a fire grate or basket about 4-6" off the bottom and difusser/water pan 12-18" above that. Like a Tall, thick walled UDS with doors
And I would definatley post pics of the Build and first Cook!