There was a balloon in one of your posts, from Fast 355, saying you need the 4.3 injectors, PROM chip and netres pack. You didn't know what he meant, (wish I did), but you already had the 4.3 injectors and PROM chip. I don't know if the reason you need the 4.3 PROM is because of number of cylinders or engine size, or both. Did you ever find out what netres pack means?
I just saw the pictures you posted - late 60s Chevy pickup? Them was purty thangs. Or maybe I just think so because they were new when I was young.