Re: Cylinder heads
There are differences in valve stem & guide diameters, and in valve head diameters. There are no external clues for these differences.

Re: Camshafts
There are seven different exhaust cam code #s, two of which were USA 1973/74 only.
There are five inlet cam codes, two were 1973/74 USA only.
The code #s are stamped into the rear face of the camshafts, and relate to the number of journals on the shafts.
Exh.: 24, 57, 71, 78 [20, 95]
In.: 25, 67, 74 [33, 91]