Any auto parts dealer should have it in stock or in their local warehouse. If that fails, John Deere used some /6 engines, on hay bailers maybe? I think Massey Ferguson or Allis Chalmers, too. John Deere can get you parts way back.
My daily driver, a 1973 Scamp 6 banger. Bought her at Chryslers @ Carlisle 2 years ago. Pretty solid old girl. Have a replacement Legendary interior for her if i ever get around to it.
That was my point. Why bother to pull a perfectly good head just to mill it to increase compression, only to give back a huge chunk of the gain to a crappy modern gasket?