This frame was last used by Dad with 4″ PVC pipe over the smaller rear toolbar.
See Ferguson Mfg. for similar parts.
12-inch disc Hiller with a 16-inch shank – Shank diameter: 1-3/16 in.
Clamps for diamond toolbar here at Pacific Ag Wholesalers.
Main Frame – 2-1/4″ square
Rear Tool Bar – 1-1/4″ square