Adopted

My take on this is that its a 400 dollar motor, the good deal part go's out the window once you start tearing into it. Next thing you know you see things that make you wanna start over because you like many might not have the experience and or experienced eyes to know what you are looking at and what if any negative effect on longevity it may or may not have. Example would be you see a line grooved on the a rod or main bearing, nothing to fuss over in a case like this...but the inexperienced worry wart will now be pulling the crank for a re grind and its a dmino effect from there.

Those 973 heads i see very rarely, mostly on van 318's from the early 80's and sometimes late 80's and they are open chamber. fwiw 302 heads didnt come on every 318 from 84' to magnum years, they used whatever head was next in the line.
Also, if 1.88/1.60 valves were installed, hope they ported them afterward...because they probably flow less than small valve stock heads!
Those piston are cast replace or stock cast.
The cam still has moly on it 'so its not even broke in' is my first thought.

My advice is aside from making sure the oil pump is good and, just run it in and enjoy your 400 dollars worth, because chances are everything ive mentioned is probably going on with this motor, the marginal crank journals, low comp cast slugs, big valve poor flowing heads from not properly blending them and some vibration around 2800-3300 rpm from a 1974 balance job.