When I built my blacksmith shop back in the mid 90's, there was a sawmill 30 miles from me that had a machine they ran 6x6 pine beams through that milled all 4 sides to your specs. Mine were curved on the outside, flat on the inside with a 45 cut on the corners, 1 inch tongue on top and 1 inch groove on the bottom. they did enough for me for a 24x40 with 10 high walls. At that time I believe they were $5000. When I got them, they all were labeled on the end to length. They also gave me an inventory sheet with a list of the logs and their lengths. We then could sit down and figure our openings using log lengths that were closest to make things come out the way we wanted for doors and windows. Unbelievably, we put all the walls up in one weekend!