It isn't hard to remove/replace the head while in the frame but there is a trick to it. With the pushrods stuck all the way in past the rockers, instead of pulling the head straight up, you use a rolling motion, and rotate the head so it ends up behind the cylinder barrel. To replace, slide the head in sideways behind the cylinder and roll it forward. I use pieces of wood to hold the head up while positioning the pushrods to save the fingers.
For years I never knew exactly how I did it. The head would magically come off after enough futzing around. I finally took the time to figure it out. But I'll probably forget how I did it for next time. Don't forget to retorque the head. I did it at 5, 50, 200, 500, and 1000 miles.
