The old SAT was not particularly difficult to coach, at least for those test takers who had deficiencies in test taking skills. But coaching and test preparation back then was not as common as it is now.
https://research.collegeboard.org/programs/sat/data/equivalence/sat-individual shows the effect of the SAT recentering.
The content of the old SAT did not really distinguish between the top end students, unless the goal was to find out who had the largest English vocabulary of sometimes-obscure words (the verbal section then was primarily a vocabulary test, with a few read-the-passage-and-answer-a-few-questions parts). The math section was just lower level algebra and geometry, so top end students typically got top end scores on that.