Might edit that last pic. HEI & tall valvecovers
Love the old pics, esp the fenders going on with the hinges attached
Also the stickers on the windshield of the '73, maybe they were used similiarly to inspection marks(?)
Have two long time local aquaintances, one worked at Fremont & other worked at Framingham, both in late 60's, early 70's. Need to quiz them some more, see if either have any old pics, or if any come out at GM retiree functions.