Differences between earlier /6 engines and newer ones

early slants had solid cams, later had hydros
early slants had spark plug tubes, new ones didnt
early slants had no intake EGR, later ones did
real early ones didnt have a alternator bracket boss on the head
came in 3 sizes, all with the same head
early ones had non emission cams, later ones did and lost power as they 'progressed'...
early ones were measured on a test stand with nothing attached, later ones were chassis dyno'd with the freakin lights on....