I prefer Head but Arch is used for conventional band sawmills, this one is stationary so I think Head is more suitable.
So I got back in the shop after supper and got carried away. Welded up the head frame. After welding up the jog in the bottom, sides, I spent well over an hr. squaring up and clamping the frame. I checked and rechecked the frame for squareness and adjusted the height of the corners many times to get the frame flat and level. Eventually I struck an arc and tacked the corners, stopped and rechecked my measurements, still good, completed welding the corners. Sorry I was so engrossed I forgot to take setup pictures.
After welding I temporarily clamped the receiver sockets over the axle hangers for support and installed the frame to see how it fits up. It was a snug fit but eventually slid right in. Here are some pictures.
The jogs in the side frame give me the right measurement between uprights for a 149" blade with lots of tension adjustment. They also prevent the slides from dropping the blade into the carriage. The closest the blade can come to the carriage is 1/2" , just enough to clear the rear dogs in the lowest setting.