[Synchro909]

I think you'll find that the square heads on those bolts are the same as the drain plugs in gearbox and diff. They are the same as a plumbing fitting which makes sense when you consider the philosophy behind Henry's design and how he wanted every farmer to be able to work on his car.
I file them down to 1/2" and I've made a special tool that is basically a short socket extension wit a nut welded to the male end. The female end goes onto the reduced bolt head and an ordinary socket on the welded nut.