I had a couple of strokes this past spring and have forgotten a lot of the finer details. From what I remember RA III was 69 and 70 only and none were casting # 16, but hey I could be wrong. As far as what year to look at with your cast date you have to remember production of a model year stops and they retool the plant for the next model year somewhere around August. As an example my current 68 convertible was produced in the 5th week of Sept. 67. With your Aug. of 69 casting date on your heads they would be for the following year and from what I remember there were no Hi/Po 16s in 70. But as you said the easiest way is to look for the screw in studs and pushrod plates and if you know what your looking at you don't even have to pull the cover because you can get a small peek through the oil fill cap with a light and a good set of eyes. Also there is no need to pull heads to look at the valves I'm pretty sure in that year if you have press in studs you have the smaller valve heads. One other note when you are looking at Pontiac heads that have been removed from an engine If you have seen enough of them you can spot 2.11 1.77 big valve heads with a glance. If you don't have experience the easiest way for a novice to tell what you have is to remember that the big valve heads have almost no space between the valve heads they almost look like they are touching. I have seen people at swap meets advertising their heads as big valve Hi/Po when they are not and with just a glance you will be able to spot the B.S. Let us know what you find. I should clarify you can have push rod guide plates with press in studs.