One other thing that's a finer point that some may find minutia. The late Milt Tenopir had a really famous quote where he said (of his offensive linemen) that "we recruit on bone structure." Although it wasn't stated explicitly, what he meant by that was examining the guy's body for its overall genetic potential to hold lean mass. This can be roughly calculated by a function of several measurements.
That was then combined with an outstanding culture of year round weightlifting. It wasn't just the lifting though, as many probably believe.
We have got to get back to that level of attention to detail.