273 commando heads vs. standard

1.1.78 or 1.87. Whatever! Enjoyed going back and forth with you on this pishta. I use to get into it with Paul Ceasrine on D/Dart stuff.
Just think, I have the original docs that appear in your last post. Got them with the latest D/Dart. I misread the o/s valve size in the 1966 parts book. It was +0.030 dia stem.
Got a call into Galen to see if he transposed the 1.78 and 1.87 in his casting book. I'll update you when I find out.