Here all the 1/2" nuts are welded on and the bottom plates are welded on the frame sockets. The bottom plates are drilled to prevent rain from filling the sockets with water. These sockets will be welded to the trailer frame. The whole head assembly and frame will insert into these sockets and locked in place with the 4 - 1/2" bolts. This also means of course that it can be removed if I need to work on it or if I decide to change something. And for a different take, if I need to haul something long and heavy, I can remove the head frame and carriage and use just the trailer and hoist to load and haul whatever item has peaked my pack rat interest, ha, ha.
The two longer pieces are the frame slides, the wheels, bearings, drive, engine, and many operating assemblies will all be attached to these slides. When making a cut it is important that this assembly is locked to the head frame to prevent any shifting which would effect the quality of the cut. To make this more convenient I would like to set up a linkage that would allow both locks to be tightened from the operating position. Something like this, we'll see when we get to it.
If I get ambitious later, maybe I'll get started welding up the head frame.